Discard the old bootstrap3theme custom navigation view which was left over from bootstrap2
Fixes issue where bootstraptheme & bootstrap3theme wouldn't save theme configuration settings correctly in some circumstances
Now allows passing a 'link' param in expTheme::head() config; allows for an array of stylesheets passed in the 'link' param for expTheme::head() or {css} smarty block; and allows for a .png favicon;