Change tools to not use files directly

[sikthehedgehog]

Currently the tools use FILE from stdio directly, but that prevents people from integrating them properly into their own code (yes, that has happened several times already, in particular with slz). So gotta refactor the tools to allow for more generic streams (even if the end they still only use files, at least they should be made easier to adapt).

The complex stuff (thinking mainly of mdtiler here) have global state which is definitely going to get in the way >_> That is going to be harder to deal with.

[sikthehedgehog]

Probably should take it further and turn all of them into libraries with the command line tools being stock frontends.