AC_Fence: Add fence floor breach checks and calculations
AC_Fence: Add event logging to enable/disable of fence floor
AC_Fence: Adjust sys_status reporting to look at total fence count
AC_Fence: Make retrieving of the return point accessible
AC_Fence: Check whether fence is enabled or autoenable is set for arming checks
Checks whether the fence is currently enabled OR if the fence is intended to be enabled automatically.
These checks are used to find out enabled fences, or prearm checks
This should resolve a problem in autotest where we don't detect the
fence as being breached as ArduPilot never announces the fact it has
breached - it just changes mode to RTL but the interval on the
FENCE_STATUS message never aligns with the time the vehicle is breached.
AC_Fence: add interface for retrieving exclusion polygons
AC_Fence: add interface to get exlusion polygons to polyfence loader
AC_Fence: add suport for inclusion circles
AC_Fence: add option for compiling-out FENCE_POINT protocol support
AC_Fence: get_exclusion_polygon and get_boundary_points set num_points to zero on failure
AC_Fence: use Debug(...) to hide debug messages
AC_PolyFence_loader: add methods to retrieve all inclusion zones
AC_PolyFence_loader: valid simply returns true if a polygon boundary can be returned
AC_Fence: add get_exclusion_circle
AC_Fence: add get_exclusion_circle_update_ms accessor
AC_Fence: PolyFence_loader gets inclusion circle accessors
AC_PolyFence_loader: add and use semaphore to protect loaded fence
AC_Fence: move fence breach check below fence type checks
This allows us to provide more information to the user about why they
are breached.
For example, if the radius is negative you are considered in breach of
it - but we'd tell you you were breached, not that your radius was
invalid
AC_Fence: clear the fence if we discover the user has set the fence count to zero
There's only one caller to this, who didn't force loading - so remove
the unused parameter.
Also remove the _boundary_loaded boolean; it was only set to true in one
place - just before the sole caller called the function!
