RFC: Add a history button to the dashboard kind of like Cacti

This pull request should supercede #123.

@spellik: Please do look over [this commit](https://github.com/SEJeff/graphite-web/commit/1c0b97f3d16c7276b69d547545f6034d670cac75). I manually squashed your 3 commits in the previous pull request and removed all of the bonzai bits while keeping your name as the author so you get credit.

I then fixed a bug in that commit where graphs without title names would show up as ``undefined 1 hour``, ``undefined 1 day``, etc uses a fancy javascript ternary operator. Since zoom support was removed, it didn't make much sense to keep the "Cacti" button, so I removed that as well and put the History button under "Graph Operations".

@nleskiw, @mleinart, and/or @obfuscurity please do give this a shot and merge if you like it. It certainly works well in master.