Git commits in Moodle 2.7.6 by Eric Merrill

commit 8012d5ad5ec4e265c7747bdb7e59fe59a4c86642
Author: Eric Merrill <merrill@oakland.edu>
Date:   Wed, 25 Feb 2015 04:18:15 +0800
Tag:    v2.7.6

MDL-47000 session: Update memcached version referecnes to 2.2.0

commit 56e9f5c16653462d00948e1bb9ec356339073150
Author: Eric Merrill <merrill@oakland.edu>
Date:   Fri, 13 Feb 2015 06:18:30 +0800
Tag:    v2.7.6

MDL-48993 gradebook: When importing new items, treat blank or - as empty