Moved dangerous helper methods out of AVMService.

Reworked handling of path lookup failures to not throw exceptions
internally, to improve performance of certain layered directory
operations.  Unfortunately there remains at least one scenario,
handling of bulk loads, and promotions of deeply nested directories in
layered contexts, in which performance is considerably less than
ideal. 

Made AVMService.createBranch() and AVMSyncService.update() perform
implicit snapshots of source tree's stores before proceeding.


git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/BRANCHES/WCM-DEV2/root@3812 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/avm/VersionRootDAO.java

@@ -68,4 +68,11 @@ public interface VersionRootDAO
      * @return The highest numbered version.
      */
     public VersionRoot getMaxVersion(AVMStore store);
+    
+    /**
+     * Get the highest numbered id from all the versions in a store.
+     * @param store The store.
+     * @return The highest numbered id.
+     */
+    public Integer getMaxVersionID(AVMStore store);
 }