cleanup GroovyDocDialog
IDEA-74428 Ability to turn on log debug categories from the GUI

* Define an action under Help menu.
* Selecting the action shows a simple dialog with a text field for
  log categories separated by new lines (however ","
  and ";" are also considered as valid separators).
* Clicking "OK" applies Log.setLevel(DEBUG) for these categories and
  persists them. Incorrect category doesn't affect anything.
* On start DebugLogManager applies the previously saved categories.
* If there were no categories, it reads them from the LogManager,
  i.e. from log.xml.
* Categories are stored in the PropertiesComponent as a single String
  using newlines as a separator.