remove "network_ai" and "network" controllers 2

we now also remove the "is_networked" attribute and replaced it with a
controller_client_id == locl_controller_client_id check. With this the
contents of [side] should be the same for every side, especialy the
server doesn't need to send differnet [side] tags to differnet clients.
And we don't have to do serversided controller tweaks anymore.
simplyfy conditional structure
rename "current_player" -> "reserved_for"
removde "player_id" side attribute

is neither used nor documented.
fix temporary mpwait user list

actualy this list is so temporary that the player will never see it, but
the 'problem' was that "player_id" didn't contain the player names but
rather playername + sidenumber which could confuse the user if we would
be able to see it.
don't overwrite "current_player" for ai sides

actualy this is a little dangerous becasue currently some code uses
"current_player" during the mp connect phase t know whether a client is
allowed for a side. TODO: fix that
more removal of "player_id"
use "reserved_for" instead of "current_player"

"reserved_for" is only used during mp_connect and is not persistent over
savegames. that name matches more to what it does.
add compabiltiy code