Autopilot is more than just an autopilot: Introducing: "property rule"

Autopilot is more than just an autopilot: Introducing: "property rule"

The autopilot has grown beyond being just an autopilot. It's
components, filters and controllers could be used to set property
values based on complex rules and driven from other property values.
That's why I chose to give it the name "property-rule".
This patch allows to define an arbitrary number of property rules under
a/sim/property-rule[n]/path
using the same syntax as autopilot configurations.