Set UID and GID to 510 when mounting www

This preps for us to add the user and group during provisioning at the specified xID.
Remove duplicate code from unmount/remount process

Now that we're managing the mounting of the drive with the UID and GID, there is no need to mount with a user sometimes and without at others
Specify a UID and GID when www-data user and group are created

This allows for better mounting in Vagrantfile as we can specify the UID and GID before the user is created
Remove wsuwp-www-mount-initial and wsuwp-www-umount-initial states

These states are no longer necessary as we now mount the drive correctly in the first place.
Merge pull request #16 from washingtonstateuniversity/16-remount

Avoid a remount of www directory during provisioning.