- Add switchable "parse only" behaviour, useful for just parsing huge files
  without having to create the attendant data structs.
- Add switchable "default to basic feature" behaviour which makes a basic
  feature out of anything it doesn't recognise.
- change zmapGFFGetFeatures() to return a GData list of feature arrays.
- improve error diagnostics.

all the time, not just when there are connections. This is because we
need to be able to signal the caller via their destroy callback when the
view has died, whether or not there are connections. The alternative is
to force the caller to deal with at least two different ways in which the
view can disappear. Required adding code to deal with what happens when
there no views left but gtk is still calling this routine.

Add better routines for returning View status, needed by zmapControl.