Resolve "Allow collection and circular attributes as endpoint targets"

Closes #53 (closed)

• Check, if collection and circular attributes can be specified as send endpoint targets.
• Add test cases to ensure correct handling.
• Update documentation, that they can be used.

ragconnect.base/src/main/jastadd/parser/RagConnect.parser

@@ -63,8 +63,8 @@ EndpointDefinition endpoint_definition_type
 
 EndpointTarget endpoint_target
   = ID.type_name DOT ID.child_name    {: return new UntypedEndpointTarget(type_name, child_name, false); :}
-  | ID.type_name DOT ID.child_name BRACKET_LEFT ID.attribute_type_name BRACKET_RIGHT
-     {: return new UntypedEndpointTarget(type_name, child_name + ":" + attribute_type_name, true); :}
+  | ID.type_name DOT ID.child_name BRACKET_LEFT java_type_use.attribute_type_name BRACKET_RIGHT
+     {: return new UntypedEndpointTarget(type_name, child_name + ":" + attribute_type_name.prettyPrint(), true); :}
   | ID.type_name                      {: return new UntypedEndpointTarget(type_name, "", false); :}
 ;