Add the ability to pass additional CSS classes to modal dialogs and
make use of this facility in form.js to annotate CBI map modals.
This can be used later by themes to apply additional CSS rules.
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
Add a new client side form.js library which is a more or less direct
reimplementation of the Lua side cbi.lua in JavaScript.
Due to its client side nature, it supports a number of features which
would be hard to realize on the server side, such as drag&drop sorting,
modal sub-map dialogs, reload-free editing etc.
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
