[plexus work] archiva-checksums

[Joakim Erdfelt]

I've been taking a stab and removing some of our dependencies on various 
plexus components.

First up, plexus-digest.
I've taken the varied code from many locations and come up with a stand 
alone archiva-checksum lib/component that I hope to be able to integrate 
into archiva/trunk.

So ... uhm ... consider this a call for discussion. ;-)

- Joakim