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.
GPS now lets the delegate handle the sequencing behaviour, by
setting a new config property. The default GPS delegate (in Nasal)
now sets this property.
This requires a corresponding FGData update.
In the initTestGlobals() helper function, the event manager is added to the subsystem manager (both
created by the FGGlobals ctor). This allows the event manager to be destroyed via the subsystem
manager in the FGGlobals dtor.
The test_suite/helpers directory has been renamed to test_suite/FGTestApi/ and
all the fgtest namespaces renamed to FGTestApi. The helper functions are now
also placed into either a setUp or tearDown namespace depending on their
function. And a new FGTestApi::PrivateAccessor::FDM namespace has been created
for holding friend classes used to access private or protected variables or
functions from solely within the test suite.
