We introduce new submenu Remote -> Remove Remote, allowing to remove
remotes. In the future, we might consider a confirmation popup to avoid
misclicks, but removing a remote is not very lossy operation.
Signed-off-by: NPetr Baudis <petr.baudis@novartis.com>
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>