Updated withHeadings to respect config definition

[MotchQF]

Settings withHeadings: true in config wasn't updating the default when new tables were created and I believe its due to being hard coded false.

[alomoa]

The bug is due to the getConfig method in plugin.js. It first checks if data exists and if it does to return the withHeadings value from that. The thing is, data object will always exist even when creating a new table, It'll just be empty. So the method will never return from config (where we set our withHeadings). A possible solution could be to have another nested if statement to check if data has any properties inside, something like if Object.keys(data).length > 0 and then proceeding to return the value from data. I tested this and it works for me.