[WIP] Add dependency injection functionality, Closes #85 (#86)

* misc improvements (as suggested by intellij)

* first draft of the DI functionality (#85)

* address review

* reenabled disabled inspections

* overload registerDependency method

* inject fields of superclasses two and remove invalid sponge default dependency

example/src/main/java/co/aikar/acfexample/ACFExample.java

@@ -78,17 +78,27 @@ public final class ACFExample extends JavaPlugin {
             }
         });
 
-        // 6: Register your commands - This first command demonstrates adding an exception handler to that command
+        // 6: (Optionally) Register dependencies - Dependencies can be injected into fields of command classes by
+        // marking them with @Dependency. Some classes, like your Plugin, are already registered by default.
+        SomeHandler someHandler = new SomeHandler();
+        someHandler.setSomeField("Secret");
+        commandManager.registerDependency(SomeHandler.class, someHandler);
+        commandManager.registerDependency(String.class, "Test3");
+        commandManager.registerDependency(String.class, "test", "Test");
+        commandManager.registerDependency(String.class, "test2", "Test2");
+
+        // 7: Register your commands - This first command demonstrates adding an exception handler to that command
         commandManager.registerCommand(new SomeCommand().setExceptionHandler((command, registeredCommand, sender, args, t) -> {
                 sender.sendMessage(MessageType.ERROR, MessageKeys.ERROR_GENERIC_LOGGED);
                 return true; // mark as handeled, default message will not be send to sender
         }));
-        // 7: Register an additional command. This one happens to share the same CommandAlias as the previous command
+
+        // 8: Register an additional command. This one happens to share the same CommandAlias as the previous command
         // This means it simply registers additional sub commands under the same command, but organized into separate
         // Classes (Maybe different permission sets)
         commandManager.registerCommand(new SomeCommand_ExtraSubs());
 
-        // 8: Register default exception handler for any command that doesn't supply its own
+        // 9: Register default exception handler for any command that doesn't supply its own
         commandManager.setDefaultExceptionHandler((command, registeredCommand, sender, args, t) -> {
             getLogger().warning("Error occured while executing command " + command.getName());
             return false; // mark as unhandeled, sender will see default message

example/src/main/java/co/aikar/acfexample/SomeCommand.java

@@ -29,6 +29,7 @@ import co.aikar.commands.annotation.CommandCompletion;
 import co.aikar.commands.annotation.CommandPermission;
 import co.aikar.commands.annotation.Conditions;
 import co.aikar.commands.annotation.Default;
+import co.aikar.commands.annotation.Dependency;
 import co.aikar.commands.annotation.Optional;
 import co.aikar.commands.annotation.Subcommand;
 import co.aikar.commands.annotation.Values;
@@ -36,6 +37,7 @@ import co.aikar.commands.contexts.OnlinePlayer;
 import org.bukkit.World;
 import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
+import org.bukkit.plugin.Plugin;
 
 @CommandAlias("acf|somecommand|sc|somcom")
 public class SomeCommand extends BaseCommand {
@@ -46,6 +48,29 @@ public class SomeCommand extends BaseCommand {
         setContextFlags(SomeObject.class, "foo=bar");
     }
 
+    // marking fields with @Dependency allows you to define  instances that should be easily accessible to commands
+    @Dependency
+    private SomeHandler someHandler;
+    // some classes like your plugin are automatically registered for injection
+    @Dependency
+    private Plugin plugin;
+    // you can even use named injections to have multiple instances of the same type
+    @Dependency("test")
+    private String testString;
+    @Dependency("test2")
+    private String testString2;
+    @Dependency
+    private String testString3;
+
+    @Subcommand("testDI")
+    public void onTestDI(CommandSender sender){
+        sender.sendMessage("The value for the injected SomeHandler is " + someHandler.getSomeField());
+        sender.sendMessage("Plugin is null? " + (plugin == null));
+        sender.sendMessage("Test String 1: " + testString);
+        sender.sendMessage("Test String 2: " + testString2);
+        sender.sendMessage("Test String 3: " + testString3);
+    }
+
     // %testcmd was defined in ACFExample plugin and defined as "test4|foobar|barbaz"
     // This means, /test4, /foobar and /barbaz all are aliased here.
     // functionally equivalent to @CommandAlias("test4|foobar|barbaz") but could be dynamic (Read from config)

example/src/main/java/co/aikar/acfexample/SomeHandler.java

@@ -0,0 +1,14 @@
+package co.aikar.acfexample;
+
+public class SomeHandler {
+
+    private String someField;
+
+    public String getSomeField() {
+        return someField;
+    }
+
+    public void setSomeField(String someField) {
+        this.someField = someField;
+    }
+}