MDL-43341 SCORM Report: spacer.gif must be managed with $OUTPUT->spacer
MDL-44141 Completion: System updates data during restore

The completion system has code which is supposed to prevent it
updating completion status while grades are being restored. This
code was a nasty hack and had not worked for some time. As a result
completion dates were restored incorrectly.

This commit implements a 'proper' way to find out if a restore is
currently running, replacing the previous hack.
Merge branch 'MDL-44141-master' of git://github.com/sammarshallou/moodle
MDL-44552 Events: Fixed wrong id returned in get_url
MDL-42890 backups: Updated help string to indicate logging is required
Merge branch 'MDL-44608-master-fix1' of http://github.com/damyon/moodle
Merge branch 'MDL-43341' of git://github.com/nobelium/moodle
MDL-42025 behat: changed behat tag _only_local to _file_upload
Merge branch 'wip-mdl-44552' of https://github.com/rajeshtaneja/moodle
MDL-44582 installer: added check for php json extension
Merge branch 'MDL-42892-master_42890' of git://github.com/ankitagarwal/moodle
MDL-43856: Add a mathjax loader filter.