Support passing language info to drag and drop setup

- Deriving langInfo moved out of createLayout() and setup initially once-and-for-all and included in layoutInfo to be used e.g. when setting up drag and drop event
- Fixed bug causing en-US lang to be (permanently) overridden by lang set in options. Use jQuery extend deep copy when setting up langInfo to ensure that English text is used if no text is given the the specified lang.