Add the uid to the CID of cached widgets.

#6252 

This PR adds the uid to the CID of the cached box so anonymous users get their own version of the cache and not the one for logged users that includes contextual links (and in the case of a "Class" the link ato ad class material).

Anonymous user gets the LOP of the the "Class" type:
![selection_265](https://cloud.githubusercontent.com/assets/4497748/3350859/309a588a-f9dc-11e3-86dd-809ab0d32c86.png)