Add jQuery.floatThead as an optional addition

[timgentry]

It would be nice to add jQuery.floatThead as an optional addition, in the same way as we provide the date picker.

We will obviously need to provide the css that makes it work for bootstrap.

[timgentry]

As a possible alternative, data framework Recline.js uses SlickGrid, for which the most active branch seems to be https://github.com/6pac/SlickGrid