DEV-34488 Can not save script to a prim. Underlying issue was LLPreview...

DEV-34488 Can not save script to a prim.  Underlying issue was LLPreview holding two member variables mObjectUUID and mObjectID.  mObjectID was null for scripts.  It appears to be used only for notecards (?), so I converted it to mNotecardObjectID and switched references to point to mObjectUUID.  Renamed one other variable to mSaveObjectID for clarity.  Removed unnecessary include files and de-inlined a couple functions because I was there.  Reviewed with Steve.