[unfinished] added organizations (only for sites)
fix
fix
fix
fix
migration for organizations
added organizations to webfrontends
fixed migration
fixed migration
fix
added organization column to users
fix
fix
orga in account now also in web
enhancetable can now filter by custom keys
fixed error message
fixes according to issue #222 comments
Merge pull request #222 from t-gerhard/master

Organizations as entities, Sites and users belong to organizations. Permission system will be adapted in a later pull request.