ResourceBundleEditor improvements:

* "add property" action in editor toolbar and context menu
* rename actions: rename property key, property group prefix, resource bundle base name in editor, rename resource bundle base name in project view
* find usages in RB editor
* delete property in RB editor
* copy provider (copy key name) in RB editor
cleanup
cleanup
resource bundle editor -- after change another property previous will save now
RUBY-6250 Rename refactoring for Cucumber step definitions