extend GetVersion to expose:

extend GetVersion to expose:
* interface :
    registry | slicemgr | aggregate | component
* peers (registry and slicemgr only)
    dictionary of (hrn => URL)
    for supporting introspection
* hrn : well, the hrn associated with this server (registry and slicemgr only)
* tag : the git tag
* hostname :

Example:
~/.sfi-vplc $  sfi.py -d . version -R
peers               : {'plc': 128.112.139.90:12345'}
hostname            : vplc10.pl.sophia.inria.fr
tag                 : sfa-1.0-6
hrn                 : ple
interface           : registry
geni_api            : 1
sfa                 : 1