Added the permissions plugin

The username and id are stored in the annotation_json column and restricted the
users to update and delete their own annotations only. This patch also changes
the column name from user_id to annotation_user_id due to the error arising while
using INNER JOIN.

Change-Id: Idefe71b7f0a991f32db94d3ee26e77943320a6b2
Merge "Added the permissions plugin"