Add to the webapp some configuration of git-annex.

There are some basic settings that pass through to git config, things like how much disk space to leave free, how many copies to ensure are kept of files, etc.

The meat of the configuration will be in configuration assistants that walk through setting up common use cases.

• Create a repository (run when the web app is started without a configured repository too). done
• Clone this repo to a USB drive or other removable drive. done
• Make a bare repo on a remote ssh server done
• Clone this repo to another host. (Needs pairing) done
• Set up Amazon S3. done
• Set up encrypted rsync remote. done
• Rsync.net special case done
• Set up gpg encryption key; gpg key distribution.
• I lost my USB drive!
• etc -- many more possibilities