annotation: first commit

Signed-off-by: Adrian-Tudor Panescu <adrian.tudor.panescu@cern.ch>
annotation: scaffolding

* Added working add/ view actions in the annotation modal.

Signed-off-by: Adrian-Tudor Panescu <adrian.tudor.panescu@cern.ch>
annotation: additions and fixes

* Fixed wrong URL for AJAX requests (was relative instead of absolute);
* Added URL detection when adding/ viewing annotations;
* No longer using dictionary for configuration parameters;
* Minor refactoring.

Signed-off-by: Adrian-Tudor Panescu <adrian.tudor.panescu@cern.ch>