MDL-45075 mod_forum: Move user subscription to an observer

The forum subscription function is called in some cases on forum creation
(specifically the case of an automatically subscribed forum).

Since the forum subscription requires both the course_module instance, and
the context these must both be present when subscribing users to the forum,
however these are not fully set up until after the forum has been created.

By moving the subscription to a subscriber, we are able to hook into the
module creation event after the course_module and context have been linked
to the forum instance.
MDL-45186 mod_quiz: Some RTL improvements on quiz edit page
MDL-45124 dndupload: Lowercase types when comparing

IE helpfull uses a mixed-case version of 'Text' which fails the string
comparison. All other browsers use lowercase for their mime-types.
MDL-45096 block_navigation: Check for existence of the siteadminbranch before modifying it

Prevents JS errors in some themes when admin block is hidden
MDL-45172 block_completionstatus: added a check for an empty string before appending
MDL-45219 remove old assignment course instance list
MDL-45219 add \mod\chat\course_module_viewed event
MDL-45219 add report_viewed event to tool_capability
MDL-45219 add report_viewed event to report_questioninstances
MDL-45219 add course recent_activity_viewed event
MDL-45134 adminlib: No more validation error when a config file is not set

When the destination draft area existed and the user draft area has not
been used, and thus does not exist, an error was displayed to the user
saying that they could not save the setting.

This was intended to handle the cases where the draft area disappears
and would overwrite the content of the destination area, deleting
all its content. But now we do not prompt with an error when
overwriting empty with empty.
MDL-45169 atto_image: Translatable string for 'size'

AMOS BEGIN
 CPY [size,core],[size,atto_image]
AMOS END
Merge branch 'MDL-45134-master' of git://github.com/FMCorz/moodle
Merge branch 'w17_MDL-45219_m27_addtolog' of git://github.com/skodak/moodle
MDL-45214 always try to use ID sort in get_events_select()

This should make PostgreSQL behave more like MySQL
and resolve the problem when events were appearing in different
order.
MDL-44928 mod_forum: Fix urls in log entries for forum events
MDL-44928 mod_forum: Add unit tests for urls in mod_forum events
MDL-45075 mod_forum: Add unit tests for forum subscription on forum creation
Merge branch 'MDL-45075-master' of git://github.com/andrewnicols/moodle
MDL-45238 event\course_viewed: Added require for course/lib.php