Implement image uploader - adding library and basic functionality

SDUX-33
Merge changes and resolve conflicts of upload-avatr branch and master
Fix requirejs loading of upload modules.
Merge remote-tracking branch 'nikola/upload-avatar'
Implement saving of user picture on profile page.

There is now upload service which returns a promise.

SDUX-39
Merge branch 'master' of github.com:superdesk/superdesk-client