Forms declarations now using String instead of Integer

  * Also fixed more compilation errors
Refactor: AnnouncementManagement now points to the External ID of the boards, instead of the idInternal
Refactor: Removed domain slots containing id internals.
Refactor: File's readByExternalStorageId now uses OID instead of Id Internal
Resolved more compilation errors
Removing Integer.valueOf in request.setAttribute
Fixing JSPs: Using the correct type and imports
Refactor: Fixed externalId.equals
Forms return an empty String as a default value. Changing the code to be aware of that
Added getDomainObject(DynaActionForm, String)

  * This way form External Id Values can be safely used, as the
    default value for a String is ""