Guide users to continue rebase/merge/cherrypick process and resolve issues

[justinrobots]

When you are in a rebase/merge/cherrypick state, we do a good job of indicating that in branch cards, but there is no path to resolve the issue.

We should guide users to open the process that is running to complete it, or otherwise explain how to resolve the issue.

[eamodio]

While a part of this is complete in 16.2 we the addition of actions to continue, skip, abort, edit. But we probably should add an action (though not another icon -- there are already too many) that will take you to the SCM view to resolve the conflicts. Maybe linkify "conflicts" in the message?