Disallow the deletion of paths that are members of file groups. To
delete a path, first remove it from all groups.
By use IAdaptable, remove the dependency we have on importing the JDT
core libraries.
Fix a bug where directories were allowed to be added onto a package
diagram (or within a file group). This was causing directories to appear
as if they were files, causing problems later on when files within that
directory were to be added.
Implement two new "Modify" operations on the Actions Editor:
  - Delete Matching Actions
  - Make Matching Actions Atomic
Additionally, create a Dialog box to help the user select the
pattern-matched actions they want to delete, or make atomic.
Implement the "Merge Actions Into Groups" function, and the associate
dialog for allowing the user to divide a set of actions into sub-groups.
Fix the "hide selected" and "reveal selected" menu items that had
accidentally dropped off the menu due to internal class restructuring.