Addresses issue #1273 (see Description)

Implements features Ivan requested.

-Database stores the label of the contributor key used to upload data on a locked project
-If the project owner views the data sets in the project, data sets uploaded with a contributor key will show a picture of a key instead of their Gravatar. The key's title attribute is the label of the contrib key used.
-Project owner can select data sets by the contributor key that was used to upload the data. Visualize & export buttons are enabled/disable based upon whether any data sets with a given contributor key exist.

All of the above features (selecting by contrib key, seeing the keys, etc etc) are hidden from anyone that cannot edit the project.

@kcarcia, It wouldn't let me update the old pull request (pushing to origin jk1273 wouldn't update the branch, not quite sure why).  Sorry!