Add support for multi word tab completion (#200)

I added support for multi word tab completion.

Current problem:
the replacement "example" contains completions with whitespaces
```java
@CommandCompletion("@example")
public void test(Player player, String takesTheRest) {...}
```
"takesTheRest" takes all the whole rest howewer the tab completion only supports one word.

I don't use the ACFUtils much and maybe there are some ugly checks, feel free to refactor.

core/src/main/java/co/aikar/commands/BaseCommand.java

@@ -685,7 +685,11 @@ public abstract class BaseCommand {
      * @return All results to complete the command.
      */
     private List<String> completeCommand(CommandIssuer issuer, RegisteredCommand cmd, String[] args, String commandLabel, boolean isAsync) {
-        if (!cmd.hasPermission(issuer) || args.length > cmd.consumeInputResolvers || args.length == 0) {
+        if (!cmd.hasPermission(issuer) || args.length == 0) {
+            return Collections.emptyList();
+        }
+
+        if (!cmd.parameters[cmd.parameters.length - 1].consumesRest && args.length > cmd.consumeInputResolvers) {
             return Collections.emptyList();
         }
 

core/src/main/java/co/aikar/commands/CommandCompletions.java

@@ -23,6 +23,7 @@
 
 package co.aikar.commands;
 
+import co.aikar.commands.apachecommonslang.ApacheCommonsLangUtil;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
@@ -191,6 +192,8 @@ public class CommandCompletions<C extends CommandCompletionContext> {
             String last = completions[completions.length - 1];
             if (last.startsWith("repeat@")) {
                 completion = last;
+            } else if (argIndex >= completions.length && cmd.parameters[cmd.parameters.length - 1].consumesRest) {
+                completion = last;
             }
         }
 
@@ -230,7 +233,8 @@ public class CommandCompletions<C extends CommandCompletionContext> {
             CommandOperationContext<?> ctx = CommandManager.getCurrentCommandOperationContext();
             return ctx.enumCompletionValues;
         }
-        if (completion.startsWith("repeat@")) {
+        boolean repeat = completion.startsWith("repeat@");
+        if (repeat) {
             completion = completion.substring(6);
         }
         completion = manager.getCommandReplacements().replace(completion);
@@ -252,6 +256,22 @@ public class CommandCompletions<C extends CommandCompletionContext> {
                 try {
                     //noinspection unchecked
                     Collection<String> completions = handler.getCompletions(context);
+
+                    //Handle completions with more than one word:
+                    if (!repeat &&
+                            command.parameters[command.parameters.length - 1].consumesRest
+                            && args.length > ACFPatterns.SPACE.split(command.complete).length) {
+                        String start = String.join(" ", args);
+                        completions = completions.stream()
+                                .filter(s -> s.split(" ").length >= args.length)
+                                .filter(s -> ApacheCommonsLangUtil.startsWithIgnoreCase(s, start))
+                                .map(s -> {
+                                    String[] completionArgs = s.split(" ");
+                                    return String.join(" ",
+                                            Arrays.copyOfRange(completionArgs, args.length - 1, completionArgs.length));
+                                }).collect(Collectors.toList());
+                    }
+
                     if (completions != null) {
                         allCompletions.addAll(completions);
                         continue;