Clicking format buttons loses selection in non-IE

At some point along the way (before 1.0.0b6), we broke selection restoration after changing the node type via selection. If you change a paragraph into a header, your selection goes poof and you have to click back in to the header. We shouldn't make people do that.
We need to document this, both in docs and in the changelog (as a backwards incompatible change). Plugins will need to know about it and so will anyone who customizes the editor. This change will break PolicyStat, for example.