MDL-42752 File-picker: Fix tabbing to disabled icons
MDL-45616 repositories: more clearly distinguish when we use source and when reference

Function repository::get_moodle_file() should always be called on packed reference and not on the source received from user.
Also added phpdocs to some other methods that were confusing source and reference
MDL-45616 repositories: use json encoding instead of serialization
MDL-45463 mod_lti: Prevent XML entity injections from provider
MDL-45417 mod_imscp: Prevent entity injections from package content
MDL-46148 qtype_calculated: fix formula validation.
MDL-45760 make sure to check permission before setting header
MDL-45683 user: Escaping Skype ID used in profile
Merge branch 'MDL-41389_m27' of https://github.com/markn86/moodle into MOODLE_27_STABLE
Merge branch 'MDL-42393-27' of git://github.com/FMCorz/moodle into MOODLE_27_STABLE
MDL-46042 badges: Clean up external badge data

Signed-off-by: Yuliya Bozhko <yuliya.bozhko@totaralms.com>
MDL-46201 events: Sanitization of username before returning the description.
Merge branch 'MDL-43347-27' of https://github.com/mackensen/moodle into MOODLE_27_STABLE
MDL-46073 badges: Make sure html tags are not used in badge description

Signed-off-by: Yuliya Bozhko <yuliya.bozhko@totaralms.com>
Merge branch 'wip_MDL-46126_m27_passnulls' of https://github.com/skodak/moodle into MOODLE_27_STABLE
Merge branch 'MDL-45678-006-27' of https://github.com/dbezborodovrp/moodle into MOODLE_27_STABLE
MDL-45678 cache: renamed new cache and better comments
Merge branch 'wip_MDL-45945_m27_mssqlcol' of https://github.com/skodak/moodle into MOODLE_27_STABLE
Merge branch 'MDL-46240-27' of git://github.com/danpoltawski/moodle into MOODLE_27_STABLE
Merge branch 'MDL-46212_27' of git://github.com/timhunt/moodle into MOODLE_27_STABLE