This change allows a Nexter to be used in the same manner as a scanner
using a for graph.Next(it) {} construction.
It is important that graph.Next(it) and any associated it.Result() calls
operate on the same iterator.
This is done unsubtlely at the moment and there is plenty of room for
optimisation of assertion location to prevent repeated reasserting as is
done now.
These packages really impact on test readability with crazy action at a
distance. In addition to this removal of goconvey reduced the test run
time for leveldb on average by about 40-50%.
We already have reference behaviour, so this is not necessary.
This change highlighted fairly baroque architecture in mql that deserves
some attention; the use of channels is somewhat confusing.
Also rename LastResult to Result.
