Git commits in Moodle 2.7.13 by Simey Lameze

commit 55ba3a26d2710ce3c5f13287b0c3538b9a934fa4
Author: Simey Lameze <simey@moodle.com>
Date:   Tue, 08 Mar 2016 16:06:16 +0800
Tag:    v2.7.13

MDL-53031 mod_assign: add session check on assignment plugins management

commit 3b214760fb51ae2b0c85bbb2b272b9bc7c164657
Author: Simey Lameze <simey@moodle.com>
Date:   Mon, 18 Jan 2016 10:13:11 +0800
Tag:    v2.7.13

MDL-50705 core_user: introduce new fill_properties_cache()

commit f4fcb1c4f76488d4571d3d265efce3813676c45d
Author: Simey Lameze <simey@moodle.com>
Date:   Mon, 18 Jan 2016 10:00:56 +0800
Tag:    v2.7.13

MDL-50705 auth_db: apply standard cleaning to all fields