Add a wp-content directory to be used as the content directory after installation

First. There are some things in the content directory that should not exist until after WordPress has been installed. We should move them over as they are required during provisioning.

Second. content/ is a crappy name for a directory whose original name is wp-content. We should keep it as wp-content so that sites can be moved to other WordPress installations with minimal effort if the need ever arose.
Move themes directory from content to wp-content
Move plugins directory from content to wp-content
Set the content directory in local-config.php to wp-content
Add a placeholder sunrise.php for use during installation

We'll copy the proper sunrise over after the network is initially setup.
Update .gitignore for the new structure
Merge pull request #4 from washingtonstateuniversity/initial-state-handling

Use wp-content rather than content as the content directory. Set things up for better install via provisioning.