Centralize enable fields in repositories

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@85190 735d13b6-9817-0410-8766-e36946ffe9aa
Fix enable fields usage

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@85192 735d13b6-9817-0410-8766-e36946ffe9aa
Add stock check for category rendering

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@85193 735d13b6-9817-0410-8766-e36946ffe9aa
Change products has stock check to respect stock handling service

git-svn-id: https://svn.typo3.org/TYPO3v4/Extensions/commerce/branches/55612@85194 735d13b6-9817-0410-8766-e36946ffe9aa