Arguments list change in addToClassPath method.

Minor: refactoring
KotlinNature reintroducing removed.

Minor: java code conventions, refactoring
Spaces instead of tabs.

Minor: java code conventions, refactoring
Adding the Kotlin runtime library by ProjectUtils class.

Minor: refactoring, java code conventions
On kotlin-ui bundle start-up suggests to add kotlin runtime library to the project (if necessary). Automatically adds kotlin nature and builder.

 #KT-3956 Fixed
 #KT-5374 Fixed
 #KT-5559 Fixed
Ignoring *.orig files.

Feel free to add any files (git add *) after resolving conflicts during rebasing.