Support thumbnails for Videos

* Add VideoEmbed::thumbnail() and rework existing embed() code
* Make reports::save_media() save video thumbnails too
* Allow grabbing video embeds without echo'ing immediately.
* Add events to allow plugins to add additional services
Fix errors when deleting media with link set to ""

Adds check to make sure we have a value in the DB before checking file
exists
Fixes for deleting feed items

* Fix #981 - SQL error when multiple items selected for deletion,
  and multiple items deleted when delete button pressed on single entry
* Fix #785 - No button for multiple delete feed items
Reduce code duplication in VideoEmbed::thumbnail()
Better handling of youtube URL without v= first #982

* Also restructing when/where service detection happens
Merge pull request #968 from rjmackay/feature/video-embed-thumbnails-294

Get thumbnails for videos
Make api?task=reports able to submit reports too #988

* Also make sure the user id is saved with report too #987
Fix indentation mix up
Redirect to login form instead of http auth prompt when a deployment is in private mode
Make all request login via http auth
Fix indentation mix up
Check if incident id exist first
Change to http_auth_login bool instead
Switch to using ORM for querying the location id
This fixes issue #994 - Category_Model::get_categories doesn't work with prefixes in the database
Edge case when RiverID doesn't return an object.

Sometimes checking if a RiverID user exists returns simply false, which isn't an object, which should be handled properly.

Fixes #995
Merge pull request #990 from rjmackay/api-report-submit-fixes

Fixes for reports submission in admin API
Merge branch 'develop' of github.com:ushahidi/Ushahidi_Web into develop
Fix wrong call for set_error function