This change allows us to use cleaner dependencies between
directories. The build system is basically rewritten in large parts
and may contain bugs.

Reviewed-by: iustinp

- Use variable with prefix instead of grep and sed
- Always run with /bin/bash

Reviewed-by: ultrotter

Files are uploaded to $prefix/sbin, not $prefix/bin

Reviewed-by: iustinp

The upload tool can be used to submit the current code to an arbitrary list of
nodes. This helps developers in easily testing their changes before submitting
them.

Reviewed-by: iustinp