128517 jvonka: REPO-874: Improve REST fwk: improve error message if a POST operation is attempted with multiple items
- rationalise the code when handling POST for an API "operation" or POST to a collection that is marked as "allowMultiple=false"
- they should now consistently return the same existing error message: "Only 1 entity is supported in the HTTP request body"
- add api sanity tests to "create site", "create rating" and some of the node op's, such as "/move" & "/copy"
git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/BRANCHES/DEV/5.2.N/root@129168 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261