Fix infinite loop when SAML was incorrectly configured.

See merge request !1170

Fix gitlab:env:info rake task.

Found doing QA.

See merge request !1169

Clear cache to prevent listing deleted branches after MR removes source branch

Closes #2272

See merge request !1160

disallow irrelevant pages by defaults in robots

capitalize URL in "Home page URL"

Update default robots.txt rules to disallow irrelevant pages that search
engines should not care about. This will still allow important pages
like the files, commit details, merge requests, issues, comments, etc.
to be crawled.