Introducing puppet-templates (alias Summonable)

These are descriptors, templates, for summoned puppets, containing
essential values like maxhp, cost of movement, and so on.
Server now advertises valid summonables to clients.

Eventually clients should be able to send their summonables to the
server, but meh.
Some files can now be read (cat command)

It's kind of perverted (the terminal wasn't really prepared for this),
but it's rather fun. I wish we thought of this more, then we could make
pipes and everything (a la Software Tools).
Rework of file->executable inheritance. Add Echo.

Now it's file<-executable, executable<-server_executable,
executable<-print.

Echo is completely pointless.
Cat now trims its args; expose a bit of Terminal.
Ls, pwd and cd are now exe file in /bin.