First throw at an angularjs based policy manager

for #19

General idea is:

* load a list of tanks for which the current user has manage
* clicking that list displays info about the tank, including policy
  info
* not done yet: clicking something makes that info editable

/cc @pads and @FND for their awareness, as we've been talking about
angular all day.

Some things I learned or noted:

* If you're using jinja2 templates you can bound the angular section
  with {% raw %} {% endraw %} to avoid conflicting with the similar
  template syntax.

* I was initially misled by ngRoute, thinking it was what I needed to
  be able to drive activity based on changes in window.location. So
  I struggled mightily to try to figure out how to get it to _not_
  require a template/partial and instead just use some part of my existing
  page. Turns out partials is what ngRoute is all about.

* Instead the (a?) right alternative is $location with a watch (see
  policymgr.js for the implementation).

* However, don't set html5mode to true when using $location as it
  requires server side support for bookmarkable URIs.

* Stackoverflow is generally better documentation for angular than the
  angular documentation _if you've already started_.

I did this out on a branch because I knew it would take me some time.
The expected next steps are:

* Implement the editor, which will PUT bags with their new policies
  back to the server

* Consider a similar interface for comps. This might not be needed as
  comps inherit from their target tank.

* Consider that this could be a manager, not just a policymgr, so
  perhaps could also do bulk mgt of tiddlers in the chosen tank.
Merge branch 'policymgr' of github.com:cdent/tank into policymgr
Extract retrieving bag information to a service.

Thanks to @FND for the promises example at:
   http://fnd.tiddlyspace.com/JavaScript%20Promises

This was initially a bit trickier at first than it should have been.
Because of the async nature of the http request, sometimes the data
would not be there when the incoming uri included the bag/tank name.
Allow editing of the bag and its pieces parts.

This is not quite elegant yet, but has a path to being
pretty good. In the future:

* It would be nice if adding members used selectize or had
  similar behavior. There appear to be a variety of ways to
  do it in an angular kind of way, e.g.
      http://jsfiddle.net/sebmade/swfjT/
* It would be nice if it were nice to look at.
* It would be nice if bags were deletable (perhaps)

The primary reason for loading all the bags and their policies at
startup time is to make it possible to have a data set which
is a unique list of all the users being used, so that they can be
used in autocompletion.
Fix bugs with policymgr

* listed bags need to pass manage constraint
* simplify show/hide routine for edit
* add link to dash
Map tank list from object to list

This makes it possible for the filter to filter on most of the
data in the tanks (e.g. the values of polices) rather than just
the names. The filter implementation works with lists only.
Fix cancelling edits

Without this change the cancel removed the view onto the data.
Add meta files for recent additions.
Add link to and content for policymgr help

This is rather limited at this point, but I'd rather
hear more about what people need to know.