Make client more linux distro friendly.

[mooskagh]

Currently it's not easy to package lc0 client with linux distros. It searches for lc0 in current directory and both lc0 and client store files in directory of binary.
For linux it's usually /usr/bin/ and it's not allowed to write there. I think we have to make it more linux friendly.

What I think would be nice to do:

1. Rename client to lc0-client (/usr/bin/client is a bit too collision-prone)
2. lc0-client should search for lc0 in PATH or cwd, not in binarie's directory.
3. There should be a way for lc0-client to specify path to lc0.
4. Probably all temporary files should be in cwd (or in some fixed ~/lc0-files?), and it would be also nice to make it a parameter both for lc0-client and lc0.

[borg323]

I think we can close this.