Code cleanup: Removal of commented code blocks
Removal of unused imports
Inputs for spike testing
Code cleanup
Static code for saving spikemonitor
Working sikemonitor
Non-parallel updates for threshold and reset

The way spikespace works doesn't allow for parallel updating of the
threshold kernel in the same way as the rest of the updaters, so this
requires a bit more work.
The reset on the other hand could be parallelised by using spikespace as
the indexer.