In this change:
1) Some code from PatchScriptBuilder is moved to DiffContentCalculator
2) The PatchScriptFactory.loadCommentsAndHistory method is splitted.
Instead CommentsLoader and HistoryLoader classes are added.
3) Use immutable objects instead of mutable in some cases
4) Remove unused fields/methods from PatchScript class
5) Remove dead code for the unused 'hugeFile' parameter
Change-Id: Ibdf0385fefa3fac20602632b9e8a3f4f48d964f6
9b376b769b