Move 'Select a Bootstrap library' drop down #223
Description
Adding a custom or bootswatch library can only happen when building a new subtheme. Therefore we should move 'Select a Bootstrap library' drop down into 'Build and enable a custom subtheme' fieldset.
We still need a drop down up the top to allow a user to select 'default' (vanilla bootstrap) or 'none' (no bootstrap, for when brought in with SASS etc) or 'XXXXX' (the Bootswatch library that the current subtheme was built with).