Implements new starterkit rest call

To overcome the obstacle of the new starterkit only being compatible with 7.2.0.
In this version the starterkits are sorted by sort order in the Our repository. If you install using the "express" method (not customized) then the first starterkit returned will be used.
Adding things to `InstallHelper` felt a bit dirty, maybe there's a better way..
If Our is down, it will fail with a log message and no starter kit will be installed.
This is IDisposable, needs a using clause