T1002049 new refactoring menu

This is unfinished work, I'm opening this to get review to the proposal.

This refactors the refactorings and changes also their command IDs to match the new package structure. The problem with this is that all user defined preferences are lost - I didn't find a way to auto migrate the preferences. Therefore I created a migration manager which seems to work fine as far as I could look. The only remaining problem is that old command IDs are not removed (so far I didn't find a way to do it) and therefore duplicate entries in the key preferences (where one entry is unused).

I would like to know if you assist the changes of the command IDs + the way how the migration manager works and if you know a way on how to remove old command IDs from the workspace.