SendableBuilder.setActuator() sets the .actuator key in the network table
so dashboards can change behavior on the client side if desired, and also
sets a local flag (retrievable via isActuator()).
Both make drive bases actuators and call setSafeState on them.
This echos back the "selected" value to the "active" key to enable dashboards
to display positive feedback to the user that the value is actually set on
the robot side.
Also fixes SendableChooser so it can be safely added to multiple tables.
Changes to "selected" in any table will result in all "active" values being
updated.
Now that adding SendableChooser to multiple tables is supported, an ".instance"
key enables dashboards to treat the same SendableChooser as a common instance
if desired.
This indicates whether or not the Sendable listeners are installed.
It is set to true when SendableBuilder.startListeners() starts the listeners,
and set to false when SendableBuilder.stopListeners() stops the listeners.
This allows dashboards to choose to change their widget display based on
whether or not the value is actually controllable.
The old headers were moved into folders because doing so avoids polluting
the system include directories.
Folder names were also normalized to lowercase.
