Fixes #128

In the interests of non-collision and multiple users, favorites files are now downloaded to a path that includes the user's b32username as well as the full path to the item (storage or share).

Previously:

`https://web-dc2.spideroak.com/storage/MGSXXZ6FMVVXY/DeviceName/Users/tommy/Pictures/best-pic-evar.png`

Would have been downloaded to:

`Download/SpiderOak/.favorites/DeviceName/Users/tommy/Pictures/best-pic-evar.png`

After this change, it would be downloaded to:

`Download/SpiderOak/.favorites/MGSXXZ6FMVVXY/storage/MGSXXZ6FMVVXY /DeviceName/Users/tommy/Pictures/best-pic-evar.png`
Fixes #160 - missing nexus7 icons

Seems that 4.2.x doesn't like a font icon mapped to \e000

Moved the generic file icon to \e027 and put the no-longer-used history icon at \e000
Fixes #173 - but also a lot more than that…

Seems somewhere along the way, refreshing favorites from within the Favorites view broke. Also, viewing historical versions from within the favourites view broke.

This caused a lot more changes than it sounded like, but I think it's all sane now.

This is a regression bug. We NEED more comprehensive tests.
Merge branch 'issue-128-storing-b32-usernames' of https://github.com/SpiderOak/SpiderOakMobileClient into 0.9.4
Merge branch 'issue-160-nexus7-icons' of https://github.com/SpiderOak/SpiderOakMobileClient into 0.9.4
merge conflict