[ticket/11755] MySQL upgrader out of date

De-duplicating code from create_schema_files, mysql_upgrader.

New file phpbb/db/schema_data which contains all the current schema data.

New function in db_tools public static function get_dbms_type_map() to make the
type map available everywhere (without requiring $db be setup already)

PHPBB3-11755
[ticket/11818] Update Symfony dependencies to 2.3.*

PHPBB3-11818
[ticket/11791] Load adm/ events from styles/adm/event/

PHPBB3-11791