Add support for reading distributor slot status. This action
is complementary to already present filter setting function.
'port' distributor message is modified to accept filter color
only (without '=on/off'), device returns selected filter state.
A wrapper function ($get_filter(...)) for Lua Controller and
condition selector for ICTA Controller are implemented as well.
Signed-off-by: Michal Cieslakiewicz <michal.cieslakiewicz@wp.pl>
