Initial work on refactoring the serial interface.
Minor API corrections.
Working UART example.
Merge branch 'master' into serial
Merge branch 'master' into serial
Fix multiple dimensions from FilterNode.

Tempoarily inserting a very large delay. Must work out why this is required and
attempt to mimise.
Stop UART threads reliably.
Make UART code pass flake8.
Updated UART example.
Changes to make the inter-packet pause of the filter executable
changeable.
Use this parameter in the UART IO.
Update uart.py
Merge pull request #77 from ctn-waterloo/serial1

Changes to make the inter-packet pause of the filter executable changeable.
Merge pull request #75 from ctn-waterloo/serial

Add basic support for Serial I/O