AngularJS-version of add prefix page

Created an AngularJS-version of the add prefix page. Links to it has been added to the prefix list (to allocate a prefix from a prefix) and the pool list (to allocate a prefix from a pool). Manual assignment is also supported, but there is no link to it so far.

It's still missing some of the flashy features such as scrolling to next relevant part of the page and animated background colors for highlighting.
Yep, that's right, I'll change that!