Update warning for old Git for Windows versions

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Update Git for Windows website

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Better distribute version checks over all week days

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Fixed issue #2356: Rebase dialog should also auto-link to issue tracker

Signed-off-by: Sven Strickroth <email@cs-ware.de>