If a player looks at you or a wall you built, you gain charge, and steal
it from them!

Then, building walls now costs 15 charge.

Nice! I love this balance tweak! And it can be changed depending on how
strong we want it to be.

The impulse is fairly weak, but it has no cooldown (of course). As long
as you can reliably click on them, you can keep dragging them around.
This builds charge.

Portal now COSTS charge, rather than gaining it, so that you bully
people until you can build a portal.

You touching a wall does not do it. This encourages teamwork / using
your walls in clever ways to gain charge.

Also allow 100 walls, and removal of all walls upon death

I love git bisect! The problem was due to me accidentally deleting a
crucial condition `is_network_master` when checking for hero_switch
input.

Hero 1 fails, probably 0 too haven't checked though. Hero 2 is fine.
Haven't tested 3.