gb_proxy: Rename gbproxy_peer to gbproxy_bvc

I cannot really read the code while it contains its historical weird
naming.  A "peer" used to be a strange amalgamation of NSE + BVC,
while in reality we can have any number of BVC on top of each NSE.

We recently started to split the peer into a gbproxy_nse_peer + gbproxy_peer.
This takes it one step further and renames gbproxy_peer to gbproxy_bvc,
as that's really what it is.

Change-Id: Iae01067282a6401f6af4cab731202872d2cdb080
8 files changed