[Feature] Allow access to the filter configuration xml.

This feature allows users to get the XML of the filterconfiguration directly, and thus allows them to edit the values directly, or more importantly, copy paste filters via text based media for working with teams, or just for sharing their favourite filter configurations.

So this will allow...

1. Users sharing filters in a team production.
2. Users sharing favourite filters as we store bookmarked filters in the kritarc, and thus everytime the configuration is reset, filter configs are lost.
3. Help users with determining how to make python InfoObjects for filters.

CCMAIL:Kimageshop@kde.org
Differential Revision: https://phabricator.kde.org/D8248