Refactoring (delegate and view proxy) classes from MapViewWidget
Review Request #123594 - Created May 2, 2015 and submitted
Separated the refactoring part of the Map Change patch posted earlier. ( to improve clarity and patch size )
This patch refactors the MapViewItemDelegate and CelestialSortFilterProxy classes from MapViewWidget.cpp to
extend their use in the MapChangeEditDialog ( https://git.reviewboard.kde.org/r/123406/ )
This does no real modification to Marble. Considered compiling it succesfully to be enough of a test.