Added feature to assign/unassign system roles stored in the CSV fields
sysrole1, sysrole2... Roles to be unassigned are prefixed with minus.

Because of a wrong merge, main $version (in version.php) was
reverted from 20150407 back to 20150402, leading to messages
about running older code than version in DB. By bumping main
$versionto 20150408 all problems should be left behind.

Conflicts:
	lib/db/services.php
	version.php

- Use correct return values types
- Fix the warnings declaration
- Fix the pluginfile URL

Conflicts:
	lib/db/services.php
	version.php

If enabled a user will be unable to make a submission unless they are a
member of a group.

Conflicts:
	lib/db/services.php
	version.php

Conflicts:
	lib/db/services.php
	version.php

Conflicts:
	lib/db/upgrade.php
	version.php

Removed requiremodintro setting from all core activity plugins and replace
with a single global setting.
Deprecated moodleform_mod::add_intro_editor and replaced with
moodleform_mod::standard_intro_elements

Conflicts:
	lib/db/services.php
	version.php

Conflicts:
	lib/db/services.php
	version.php