[feature/migrations] Rebuilding migrations data on develop

So this is easy to merge later.

PHPBB3-9737
[feature/migrations] Replace database_update.php with migrations updater

PHPBB3-9737
[feature/migrations] Revert schema for migration data

PHPBB3-9737
[feature/migrations] Remove hardcoded language, use lang instead.

PHPBB3-9737
[feature/migrations] Make depends_on static to call it without dependencies

Move installing migrations to migration/install.php and handle figuring
out what migrations have been installed based on phpBB version.

PHPBB3-11318
[feature/migrations] Fix migrations installer, schema for schema_data.sql

PHPBB3-11318
[feature/migrations] Order the migrations schema in schema_data.sql

PHPBB3-11318
[feature/migrations] Comments for the return in the custom functions

PHPBB3-11318
[feature/migrations] effectively installed check for migration data

PHPBB3-9737
[feature/migrations] Automatically populate migrations table on install

PHPBB3-9737
[feature/migrations] Reports table schema changes in recent develop

PHPBB3-9737
[feature/migrations] Subdirectories for migration data

Organization will set you free

PHPBB3-9737
[feature/migrations] Correct depends_on

PHPBB3-9737
[feature/migrations] Remove user_msnm migration

PHPBB3-9737