[ticket/13126] Improve the feedback when running the migrations

PHPBB3-13126
[ticket/13126] Extends migrator_output_handler instead of using a closure

PHPBB3-13126
[ticket/13126] Move migrator_output_handler to an interface

PHPBB3-13126
[ticket/13126] Change messages verbosity levels

PHPBB3-13126
[ticket/13126] Fix tests

PHPBB3-13126
[ticket/13126] Add missing use statement

PHPBB3-13126
[prep-release-3.1.0] Update version to 3.1.0
[prep-release-3.1.0] Prepare Changelog
Merge remote-tracking branch 'Nicofuma/ticket/13126' into ticket/13211
[ticket/13211] Add log wrapper for writing database updater to log file

PHPBB3-13211
[ticket/13211] Move console migrator output handler to db folder

PHPBB3-13211
[ticket/13210] Use the correct config value

PHPBB3-13210
Merge pull request #3061 from Elsensee/ticket/13210

[ticket/13210] Use the correct config value

* Elsensee/ticket/13210:
  [ticket/13210] Use the correct config value
[ticket/13211] Also use log wrapper output handler for console migrations

PHPBB3-13211
[ticket/13211] Move console migrator output handler back to console folder

PHPBB3-13211
Merge commit '078e0c1e440f7f906b670348e8da00141e245876' into prep-release-3.1.0

* commit '078e0c1e440f7f906b670348e8da00141e245876':
  [ticket/13211] Move console migrator output handler back to console folder
  [ticket/13211] Also use log wrapper output handler for console migrations
  [ticket/13211] Move console migrator output handler to db folder
  [ticket/13211] Add log wrapper for writing database updater to log file
  [ticket/13126] Add missing use statement
  [ticket/13126] Fix tests
  [ticket/13126] Change messages verbosity levels
  [ticket/13126] Move migrator_output_handler to an interface
  [ticket/13126] Extends migrator_output_handler instead of using a closure
  [ticket/13126] Improve the feedback when running the migrations
[ticket/13215] Update Symfony components to v2.3.21.

PHPBB3-13215
[ticket/13207] Add default subscription options for newly registered users

PHPBB3-13207
[ticket/13207] Move default user notifications settings to user_add()

PHPBB3-13207
[prep-release-3.1.0] Add 3.1.0 gold release migration