Try harder to open GitHub links

Links that can't be opened by the app will try to get as close as
possible.

For example, if the app can't open
https://github.com/github/android/issues it will try to open
https://github.com/github/android/ and then https://github.com/github/
Remove the UrlLauncher class and treat all URIs in the UriLauncherActivity class
Remove tests that use the removed UrlLauncher
Fixed Greek Translations
Merge pull request #613 from jonanp/links

Add alternative when failed opening some links
Revert "Revert "Add forking support""
Merge pull request #626 from github/revert-614-revert-612-fork

Add possibility to fork a repository
Added Swipe-to-Refresh
Clarified the 2FA toast error message
Added missing strings for the Swedish language and corrected misspellings
slovak locale updated

Signed-off-by: Adrian Matejov <a.matejov@centrum.sk>
Merge pull request #620 from iKotsos/GreekTranslationFix

Update Greek translation
Merge pull request #630 from Dajo90/swedish-translation

Update Swedish translation
Merge pull request #629 from Dajo90/2FA-toastmessage

Add a more clear message to the 2FA toast error
Merge pull request #631 from Adman/slovak

slovak locale updated
Merge pull request #619 from iKotsos/Swipe2Refresh

Add swipe-to-refresh to list items