Merge duplicated users from LDAP and import scripts

Add merge feature:
    Keep the LDAP user and merge the roles of user which from import scripts
    into LDAP user.
Do merge when user login.
Run django datamigration to merge the uesrs exist in database.

Fixes: #1921

Change-Id: I7c0ff8a605ad9cf030b9a75348d431b832aaa7bd
Signed-off-by: gaoxuesx <xuesongx.gao@intel.com>
Merge branch 'devel' of /home/nemo/workspase/iris-panel into devel