Upgrade to Gitolite v3 on puppet-git.lizard

Originally created by @intrigeri on #10093 (Redmine)

Gitolite v2 is not in Jessie.

The main difficulties I expect are: hooks handling (we do complicated stuff there), and migrating from ADC to some replacement.

Resources:

• http://gitolite.com/gitolite/migr/
• https://github.com/sitaramc/gitolite-doc/blob/master/archive/migr.mkd
• https://github.com/sitaramc/gitolite-doc/blob/master/archive/g2migr-example.mkd

Related issues

• Copied to #14587 (closed)