update version & packages

- use date as version string
- use the latest snapshot
- added app-editors/vim
- added sys-devel/bc (kernel build requirement)

Signed-off-by: Ivan Vecera <ivan@cera.cz>
zfs support

- added keywords for zfs
- added zfs packages
- modified version string to contain '-zfs' postfix

Signed-off-by: Ivan Vecera <ivan@cera.cz>