Cleanup some gravatars module odds and ends
Merge branch 'master' of https://github.com/geekwright/XoopsCore

Conflicts:
	htdocs/modules/gravatars/admin/index.php
Merge upstream/master
System module updated to doctrine, adding schema support

Modules can specify $modversion['schema'] to specify a portable schema definition to be used instead of the mysql.sql file.
Add supporting classes in Xoops\Core\Database to deal with schema
Add Xoops\Core\Yaml.php for portable schema handling
Merge pull request #26 from geekwright/master

System module conversion to Doctrine DBAL