Added button to toggle the Graph column in the History view
Created originally on Bitbucket by monotoli (Andy Lee)
Was already merged in Bitbucket before import, marked as merged by the import user
Populating the 'Graph' column can be quite slow (45+ seconds for some of our older files) when viewing the history of a single file due to the large number of 'hg parents' performed by FileParentProvider. Added a button to hide/show that column as an option for improving performance.
Also added a try/catch to catch an exception that occurs when loading graph data for certain files in our repo that have been renamed multiple times.