Monticello: Remove dead code

[jecisc]

Here is a list of changes:

• Remove unused topological sort of ancestors
• Clean MCCacheRepository (2 unused vars and some methods and removed MCPackageCache with it)
• Remove unused backport feature
• Remove MCConfiguration with its reader, writer and browser because it seems really legacy and an ancestor to Metacello
• Remove unused MCFilteredVersionSorter
• Remove MCD format that seems to be a format to export diffs but this seems unused also
• Remove unused version inspector
• Remove MCSubDicrectoryRepository that seems unused
• Merge some classes together (only one was used)
• Remove MCVersionHistoryBrowser that seems unused

This one goes with this change: pharo-spec/NewTools#610

[jecisc]

Lot of code is used only by Gofer.. We'll need to clean this one aswell