- Rather than defining the urls where they are gotten (python sysa,
python sysc, inside sysc), a spec file is now used that is easily
interpretable and tool-independent.
- This is interpreted by rootfs.py and inside sysc.
- This is also used to make sources available and extract sources.
- Manual dirname selection is no longer required as is tarball renaming
upon download - all of this is handled automatically.
Fixes#188
This allows creating *.checksums files instead of checking against
them when UPDATE_CHECKSUMS is set to True in bootstrap.cfg.
The checksums are also copied to /usr/src so they can be accessed
easily after the bootstrap completes.
