Create home sector

This is another large pull request that has the following features:
* Add sectors and clusters (groups of sectors)
* On the webpage, after login, the user can click a link to add a home sector
** This asks for the user's planet name
** When the name is entered, an empty sector is found for the user
** The planet is created in that sector
** The user is moved to that sector

The best way to test this is to fire up the tornado app, login to the site, and follow the on screen prompts to establish a home sector. Once this is done, you should see that your player is in a sector (back at the main page for the site)

If that went well, then you can verify everything created successfully by looking in the data/universe dir and poke around there.