Marker: just update the selected row all the time
We had complicated logic about when to update Marker's preview when annotator closes. We got wrong in many cases (Issue #1966 (closed), and Issue #2136 (closed), maybe others). Instead just always update the currently selected row.
If it does not need updating, then no harm done [*].
[*] I think: the interaction here with background uploader if wonky like everything else about bguploader.
Fixes #2136 (closed). Fixes #1966 (closed).
Rename function, sensible docs, log a special case
The docs didn't read right to me: checked and fixed.
Not clear what we should do on unselect: left a todo for that. For now
it logs.
After I did !1450 (merged), I tried to refactor a bit: this is result. Can be applied after !1450 (merged) or by itself (its got !1450 (merged) commits here too).