Refactored Input/Output with host based Simulator

~~... and a fruit reduction.~~

* Refactored Input/Output
* Host-based simulator for Nodes, Node->Node connections (with transforms and filtering)
* Examples corrected to use new syntax, and `synapse` over `filter`
* Refactored SDP Rx/Tx C applications
* Some neatening of directory structure (`collections.py` now in `utils/bins.py`)

@tcstewar You will need to test the serial interface as I don't seem to be getting anything meaningful from the USB port :worried:

*To do in later PRs* -- I'd like to get this pulled in first:
* Refactor vertex code to reduce duplication
* Documentation, documentation, documentation
* Modify location of binaries with a view to distribution with the package `pip install nengo_spinnaker`