Added/tweaked some UPC error logging messages
RAZ-3104: Import AD users throws error when run and no users available to import
- Fixed error message thrown when no users are available to import but 'Select all' checkbox is selected
- Tweaked code to disallow importing AD users without emails
- Added status column to UI depicting whether user has already been imported into system or not
RAZ-3106: Adding a user in administration UI with a group selected throws error
- Fixed error in admin with user not being entered in database first before calling adding of groups
- Added a note to user interface informing users on how to delete admin users properly
Handled missing file errors when downloading assets in folder
RAZ-3107: Mp4 upload would fail when MP4box was enabled (under some installations)
Merge branch 'feature/RAZ-3104' of github.com:razuna/razuna into develop
Merge branch 'feature/RAZ-3106' of github.com:razuna/razuna into develop

Conflicts:
	global/translations/English/HomePage.properties
Merge branch 'develop'

* develop:
  RAZ-3107: Mp4 upload would fail when MP4box was enabled (under some installations)
  Handled missing file errors when downloading assets in folder
  RAZ-3106: Adding a user in administration UI with a group selected throws error - Fixed error in admin with user not being entered in database first before calling adding of groups - Added a note to user interface informing users on how to delete admin users properly
  RAZ-3104: Import AD users throws error when run and no users available to import - Fixed error message thrown when no users are available to import but 'Select all' checkbox is selected - Tweaked code to disallow importing AD users without emails - Added status column to UI depicting whether user has already been imported into system or not
  Added/tweaked some UPC error logging messages