Remove debug messages.
Add setup file to provide environment variable `SPINN_NENGO_DIRS`.
Change from zeroing the accumulator to applying a mask.
Use input accumulator masking in the Ensemble.
[Bugfix] Need to convert back from `uint` to `accum`/`value_t`.
And a semicolon.
Merge pull request #19 from ctn-waterloo/reset-input-filters

Mask input accumulators to save a branch
Merge branch 'master' into nengo_spinnaker-refactor-multi-filters
Merge branch 'master' into nengo_spinnaker-refactor-multi-filters

Including work on masking input accumulators.

Conflicts:
	nengo_spinnaker/ensemble_vertex.py
	spinnaker_components/ensemble/ensemble-data.h
	spinnaker_components/ensemble/ensemble-input.c