Add batch names to claim codes, printable handouts

This PR resolves #184.

Admins can now (optionally) assign names to the batches of claim codes that they generate. This will allow them to execute actions on specific batches.

Here's an example of the claim code generation form with this PR merged:

![screen shot 2013-06-06 at 8 41 06 am](https://f.cloud.github.com/assets/124687/617913/846193c8-cea6-11e2-9158-a99eef5db697.png)

And here's the new "bulk actions" form at the bottom of the claim code management page:

![screen shot 2013-06-06 at 9 56 17 am](https://f.cloud.github.com/assets/124687/618281/019652ac-ceb1-11e2-9703-dae2e9737219.png)

The supported bulk actions are exporting distributable claim codes to a text file, and exporting them to a printable handout that looks like this:

![screen shot 2013-06-06 at 3 50 15 pm](https://f.cloud.github.com/assets/124687/620366/7a8d9586-cee2-11e2-828d-280d256c1b0f.png)

The `OPENBADGER_CLAIM_URL_TEXT` environment variable must be defined in order for the handouts to have a URL on them; otherwise they just say "go to the website" rather than e.g. "go to csol.org/claim".

We can add more bulk actions in the future, such as showing statistics on how many claim codes in a batch were actually redeemed, and so forth.