Learning Block - Fix for errors in Moodle 2.5.1 and 2.6

1) Fixes a couple of PHP notices in Moodle 2.5.1
2) Fixes a number of variable and functions that needed to be initialized before they are used in Moodle 2.6.
3) Added security check in ajax_bridge to address Moodle warning
4) Duplicate string definition removed
5) Git version is now in sync with the version published on Moodle.org which seemed to be more recent.

Signed-off-by: Michael Milette <michael.milette@instruxmedia.com>