Implement 'git-pw list'
Implement 'git-pw list'

Yet again, this is not complete but does offer a good starting point.

There is a lot of duplication introduced in this patch - duplication
which will be cleaned up in future changes.

Signed-off-by: Stephen Finucane <06fa905d7f2aaced6dc72e9511c71a2a51e8aead@that.guru>

stephenfin/git-pw,getpatchwork/git-pw