Improvements

[carkod]

Add commit data for releases table
Refactor back-end and front-end to merge into single source of data (all prod, staging domains and repos info are in one place)
Add test for domain-info endpoint
Remove some sites that are down (no jenkins job), archived (github repo) or obsolete (don't exist anywhere).
Removed sites that will not be supported because they have been moved to ubuntu.com (e.g. partners.ubuntu.com, tutorials.ubuntu.com)