let sockets broadcast values on sitelocal multicast

also, make them not use linklocal addresses as source when possible,
since this makes routing impossible.
libhexabus: join multicast group for receive commands
throw out the hexabridge. we have ascended to the next layer.
port applications to new multicast group
Merge remote-tracking branch 'origin/development' into bs-routing

Conflicts:
	shared/hexabus_definitions.h
renamed to libhexabus
workaround for include :(
Merge branch 'development' into bs-routing
initial commit - midi test
add prototype implementation of MLDv1
set multicast hop limit in libhexabus
send MLDv1 report packets to correct address
implemented midi interface.
move MLD to own file, add function to send MLD "done"
add a process for MLD, finish MLDv1 preliminary implemention
extend mld timeout calculation to 32 bit types
don't send invalid MLD packets

sending from :: yields invalid packets, so just drop these. also, don't
send reports for FF02::1, since we can neither explicitly join nor leave
that group anyway.
implemented basic midi callback infrastructure - works.
simple button callback implemented.
midi interface is functional, event abstraction implemented.