Picklist WIP: ngRepeatReorder demo nigh-verbatim

The only difference is that I deleted the ng-app="..." attr and turned
the demo module into a controller. Apart from that, it's the same demo
as the one on Codepen.

This is for testing purposes only and should not end up in production.
Add angular-sortable-view directive (MIT license)

Source: https://github.com/kamilkp/angular-sortable-view

This has no dependencies at all, unlike ngRepeatReorder which depends on
hammer.js and angular-hammer. Since ngRepeatReorder was failing on some
browsers on Windows (for example, the latest (as of this writing) stable
version of Chrome), and it was failing in a way that suggested that
event handling (of drag events, specifically) was the cause, we're going
to try replacing it with a directive that has no dependencies on other
libraries at all.
Picklist WIP: remove ngRepeatReorder demo

We're switching to a different base library, so let's remove the demo of
the ngRepeatReorder module that we're not going to use any longer.
Picklist: swap out which internal directive we use

Replace ngRepeatReorder with angular-sortable-view instead, since it has
fewer external dependencies and should be more reliable.
Picklist: rotate element being dragged 4 degrees

Also make the placeholder a lot dimmer, so it's easy to visually
distinguish it from the actual element being dragged.
Merge branch 'feature/picklist'

New features in picklist branch since last merge: changed which Angular
directive we're using for the drag-and-drop list rearranging. This one
has fewer dependencies and a lot fewer glitches (especially on Windows,
where the other one proved all-but-unusable on certain browsers).