- updates underscore to 1.5.2 and backbone to 1.1.0

backbone had some breaking changes:
- fix url/urlRoot handling in models & collections
- options are no longer attached to the view by default
- collections reset when 'fetch' is called, tell it to keep the existing
  models

other changes:
- fix some events triggering multiple times in connection with deleting
  a model
- use document fragments instead of an element array for stream entries
- adapt jasmine and cucumber specs to the changed code
  * no longer test the backbone router as part of our code
  * jasmine factory already returns model instances, no need to wrap
    that again

and comment presenter

change naming a bit to be more general since its posts+photos now
(re #3158)

Revert "Revert "refactoring backbone urls""

This reverts commit 838da1fd.

Revert "revert 9b1d64bb as it is causing inf. scroll to break (stream model now has a post collection)"

This reverts commit 2a69c0eb.

revert 9b1d64bb as it is causing inf. scroll to break (stream model now has a post collection)