Add scroll height indicators to Flickable

Since parameter system will pop message based on meta data

Fact* espVersion = getFact(FactSystem::ParameterProvider, MAV_COMP_ID_UDP_BRIDGE, "SW_VER"); crashes unit test if the parameter does not exist (which is exactly what the call is trying to establish).

Also, added a missing method on AutoPilotPlugin as a public
pure virtual method (the inheritances already implemented it as a
slot, so the new Signal syntax didn't worked because the base class
didn't had that method)
Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

First commit of modernizarion of Qt signal connections,
the new signal connection is very userfull because of a few
nice things:

- it's checked at compile time instead of runtime
- it can connect to any function or method, so we don't need
to use slots anymore
- it's way faster because it doesn't need to work with string
comparisson, but it's basically a direct call.
Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

Users are getting confused because we are missing images. Will put back
new fancy version once we get new airframe config plus auto-generate of
images sorted out.

At that point the vehicle is gone, so need to to clean it up

Takes less real estate and flows better and small displays