Bookmark loading issues

I noticed that source mode used an undefined function call while trying to load bookmarks. This wee commit fixes it but I want to make sure I'm not tripping up on the relationship between the Editor and the MapUtils view at all...

I also could not seem to locate any code in style mode that appears to even try and load bookmarks. Not sure if I'm missing anything but happy to work that in if it is in fact missing.

Not sure how/if this relates to https://github.com/mapbox/tm2/issues/444. cc @samanpwbb