Made the flagging of merged entries more clear and avoided use of
In a CompoundEdit compact a sequence of Remove&Insert Edits into a
Moved a premature call to getLastEdit() in getMergeEdit(). This is a
Moved reference to UndoManager in each Edit instance to parameters of
More restricted visibility of inner classes of UndoManager to make it
Dropped the artificial limitation to 1024 chars on expanding the gap
Avoided unreasonable memory consumption by duplicate String instances
Removed unnecessary local variables. This is a minor code cleanup part