v2v: Let source.s_name be the renamed guest name (in case we use -on option).

The original guest name is saved in s_orig_name, although I checked
all uses of s_name and nothing needs it at the moment.
v2v: Add --network and --bridge options to perform network name mapping.
v2v: Add --print-source option.
v2v: Reorder sections in the manual more logically.