Replace default builtby email, s/@vyatta.com/@contributors.vyos.net/
Replace occurences of "vyatta" and "VSE" from mk.livecd.functions

Also change version format to "VyOS x.y.z" and description
format to "VyOS z.y.z ($branch)".

version file should contain numeric version only now, the rest is
added automatically.
Replace "testing" repo with "unstable" so we can test release builds,
until we finalize the repo structure.
Replace version to numeric 0.0.1