remove "network_ai" and "network" controllers 2

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

is neither used nor documented.
fix temporary mpwait user list

actually 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

actually this is a little dangerous because 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. The new name matches more to what it does.
add compatibility code
add comment
don't generate "user_description" on the host

the host it not capable to generate strings in the correct language.
("(Reserved for $playername)" was resolved on the host). Instead we now
generate the description on the clients.
don't overwrite "name" in mpconnect

and also remove unneeded code.
we not don't overwrite "name" (the name of the leader) in mp connect if
it given by the scenario.
We also fix a previous commit "don't generate 'user_description' on the
host" which caused that the AI algorithm wasn't shown to the clients.