build: Save version from snapshot

Version is needed for live images.
buildlive: Load support index file

Load support index file and check whether the live profile is available
and has all required keys.

Issue: #27
buildlive: Save version from snapshot

Save version, will be used later to expand support files.

Issue: #27
buildlive: Rewrite support files with image information

Expand support files by replacing variables with image information from
the JSON index file and snapshot.

Issue: #27