[Lua]Harden vessel dereferencing

[TheGondos]

This PR adds checks on the "self" parameter when a Lua command executes a virtual function on vessel objects.
Prior to this, there were opportunities for CTD when the user forgot to use the ":" notation when calling a vessel method.
A proper Lua error is now propagated when we try to convert a non vessel object to a VESSEL *.
Orbiter vessels providing Lua bindings have also been updated to check for proper type before casting userdata to VESSEL objects.
Note : luaL_checkudata is not used in the interpreter because we cannot know what type of vessel is to be expected. Instead a set of VESSEL objects is maintained and checked against to test if a userdata is associated with a known vessel.
This method is robust to vessel deletion. If for example you do
v=vessel.get_interface("ISS")
then delete the ISS from the scenario editor
then
print(v:get_name())
it generates an error instead of a crash.