Added Error Log code to record errors when import fails

Added Error handling to Import so that Change Manager is turned-on after Import whether it is successful or not.
Don't allow import if the Referenced Objects have not been selected.
Turn On Change Manager if there are no active sessions
Don't crash if the Referenced Objects are not set when you right-click on a Working Draft.

PROMS/VEPROMS.CSLA.Library/Extension/DocVersionExt.cs

@@ -209,7 +209,7 @@ namespace VEPROMS.CSLA.Library
 		{
 			get
 			{
-				if (DocVersionAssociations == null) return false;
+				if (DocVersionAssociations == null || DocVersionAssociationCount==0) return false;
 				ROFstInfo roFstInfo = ROFstInfo.GetJustROFst(DocVersionAssociations[0].ROFstID);
 				RODbInfo rdi = RODbInfo.GetJustRODB(roFstInfo.RODbID);
 				string rofstPath = rdi.FolderPath + @"\ro.fst";