Project tree refactoring fixes

Fixed tons of errors and unsupported cases, mainly in the Move command. Should fix issues #144 #162 #187 #400 #518 and several more issues not reported.
Rename command left modified files unsaved, while Move command saved them, the latter is the common approach taken, and I'd say seeing tons of files with unsaved changes may confuse the user, so made Rename to behave the same.
The Move command tried to keep modified files open, but the code was wrong, I fixed the initial check but left it commented, I think it pollutes the user interfaces when the refactoring affects many files. If this feature is wanted it would require some further changes.
When the Move and Rename commands finish, the affected files that were initially open are kept open, although the position is lost.
Removed calls to RefactoringHelper.GetSearchPatternFromLang and use Project.DefaultSearchExtension instead, that way everything is centralized, this allowed to see the default search filter of Haxe projects was missing the recently added .hxp files (confirmed to be an oversight), and made finding references able to find matches in code sections of MXML files (no extensively tested).
Made folder-package check case-sensitive, as it's the right thing to do.
Could you please elaborate? If you say so because the other fields in the class are set through the constructor, well, I didn't follow that way because I didn't want to make a "constructor party" (changing the current ones would break compatibility), but if you mean this, no problem with it, I could add it.

If you mean adding a simple public variable, well, when a class already follows that way I don't mind doing the same, but in this case where it's the first property to be added, I'd rather prefer not to do it, because if you ever need to add logic, a simple variable not only isn't enough, changing it to a property causes a binary incompatibility.