From Ilka:

Changes in the fit panel functionality as follows:
- implemented as a modeless dialog, i.e. when open
it does not prevent users from interacting with other windows
- it is a singleton application, created per root session
- users can select an object for fitting in the usual way, i.e.
by left-mouse click on it; it the selected object is suitable
for fitting, the fit panel is connected with it and users can perform
fits by setting different parameters and options
- it is included in the ListOfCleanups and has the RecursiveRemove
method to handle cases of deletion of the currently selected object
or of he pad where this object is drawn


git-svn-id: http://root.cern.ch/svn/root/trunk@16761 27541ba8-7e3a-0410-8455-c3a389f83636