Fix conflicts between non-committed and external changes

[manuelma]

Re #2300

If the user presses the Refresh button in DB editor with non-committed changes, and there are external changes (already committed to the DB by somebody else in the meantime), then there might be conflicts.

We could either disable Refresh when there are uncommitted changes (as in master), or report the conflicts and let the user resolve them. I like the latter, but can be time consuming.

At the moment 0.8 always allows refreshing and just resolves conflicts automatically and silently favouring local changes. We could see how we are doing with time and priorities with 0.8 in the short-term and decide at that point?