Performance improvements for loading complex content instances

git-svn-id: http://svn.flexive.org/repository/flexive/trunk@2987 d35d4baa-7912-0410-b0ae-edacad209e15
Flat storage: fix for content reference counts of contents with multiple versions

git-svn-id: http://svn.flexive.org/repository/flexive/trunk@2988 d35d4baa-7912-0410-b0ae-edacad209e15