Ensure changes from Nasal are picked up by delegates (such as GPS) when
they are made. Add a route-manager test which sets and exits a hold
using Nasal.
As part of this, update the test API to make it easy to run Nasal from
a test.
The GPS/RNAV system can now fly holds, both left and right-handed.
The correct entry is selected, and hold count can be selected.
Also there's lots of lovely test cases.
