[git] Guess Git root a little better.
[log] Make "Show Branches Panel" action dumb aware
[log] Rewrite filtering & migrate from GraphFacade to VisibleGraph

New VcsLogFilterer to use SingleTaskController to make a single visible
graph update even for multiple refresh/change filters/request more
commits actions.

Instead of delegating to the GraphFacade of the DataPack send the
updated VisiblePack (containing the VisibleGraph and the reference to
the actual DataPack) to the UI.

Merge GraphTableModel with AbstractVcsLogTableModel;
GraphCellRenderer with AbstractCellRenderer
since there is only 1 implementation now.

This fixes the following issues:
IDEA-125278, IDEA-119054, IDEA-124822, IDEA-115917, IDEA-123885,
IDEA-123426, IDEA-115486, IDEA-115479
[log] simplify: move EMPTY DataPack instance to the DataPack
common workingTreeChangeStarted and finished methods moved to dvcsUtil from GitUtil
annotation added
mark directory dirty optimized for Hg actions
Hg UpdateTo successful execution changed

* error shown only when execution failed at all;
* warning shown only if there are unresolved conflicts;
* error util method added for 3-state exitcode commands and fail identification improved
IDEA-127320 Hg: Notify about starting and finishing VCS operations which modify the working copy files

* rebase command optimized