[feature/migrations] Basic migrations with schema and data changes

The migrator takes care of applying migrations as necessary.

RFC: http://area51.phpbb.com/phpBB/viewtopic.php?f=84&t=41337

PHPBB3-9737
[feature/migrations] Store start and end time of migrations

PHPBB3-9737
[feature/migrations] Return schema changes in database update style array

Returning the set of schema changes allows potentially aggregating to generate
the overall install schema automatically from a set of migrations

PHPBB3-9737
[feature/migrations] Standard vars for migrations and run sql with feedback

PHPBB3-9737
[feature/migrations] Moved database_update info to individual migration classes
[feature/migrations] Some migrations data

PHPBB3-9737
[feature/migrations] 3.0.8-rc1 migration, fix some calls

PHPBB3-9737
[feature/migrations] Migrations back through 3.0.6

PHPBB3-9737
[feature/migrations] Use $this->db

PHPBB3-9737
[feature/migrations] Depend on part2

PHPBB3-9737
[feature/migrations] Update 3.0.3-3.0.5 migrations to work
[feature/migrations] Rename classes, depends on

PHPBB3-9737
[feature/migrations] Change migration data processing to run step by step
[feature/migrations] Remove references as it is now 3.1 code

PHPBB3-9737
[feature/migrations] Process migration steps and move to PHP5 code
[feature/migrations] Move migrator to service container

Version numbers

3.1 updates

Restore database_update.php file to what it was in develop

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PHPBB3-9737
[feature/migrations] Update phpbb_db_migration class for PHP 5.3.3

PHPBB3-9737
[feature/migrations] Update phpbb_db_migrator class for PHP 5.3.3

PHPBB3-9737
[feature/migrations] Add method and property visibility, use __construct()

PHPBB3-9737
[feature/migrations] Migrations now somewhat works

PHPBB3-9737