Change "checkin" usage to "check_in".
Update URL parameters to the "_id" form.
Add support to checkout and check in multiple documents.
Optimize queries that used an ID list of documents for
filtering using values_list('pk', flat=True). These
queries now use .values('pk') as a subquery.
Add pre save hooks to block new document version uploads.
Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>
