[ticket/11604] Skip installer step where config.php is created.

PHPBB3-11604
Merge remote-tracking branch 'nickvergessen/ticket/11603' into develop-olympus

* nickvergessen/ticket/11603:
  [ticket/11603] Throw RuntimeExceptions instead of using exit()
  [ticket/11603] Avoid using cURL
  [ticket/11603] Split api_request into two functions (query only vs. full url)
  [ticket/11603] Fix spacing and add some comments
  [ticket/11603] Fix github API calls
  [ticket/11603] Rename network to forks and fix handling
  [ticket/11603] Fix github api url and use curl with valid user agent
Merge remote-tracking branch 'nickvergessen/ticket/11603' into develop-olympus

* nickvergessen/ticket/11603:
  [ticket/11603] Fix out dated comment
  [ticket/11603] Fix usage note
Merge remote-tracking branch 'bantu/ticket/11604' into develop-olympus