RPC debug logs don't use base64.
RPC debug logs don't use base64.

This decreases log size 27% in a simple test, and more importantly makes the
logs human readable and searchable.
Fixes #1031

Also, change corrID to an 8-byte value and break dependency on NewToken().
Fixes #909

ZCloud-Firstserver/boulder,ZCloud-Firstserver/boulder,bmw/boulder,jfrazelle/boulder,hlandauf/boulder,mehmooda/boulder,letsencrypt/boulder,jfrazelle/boulder,jcjones/boulder,ibukanov/boulder,bmw/boulder,r0ro/boulder,patf/boulder,ibukanov/boulder,benileo/boulder,jfrazelle/boulder,jcjones/boulder,letsencrypt/boulder,benileo/boulder,sophie-h/boulder,letsencrypt/boulder,sophie-h/boulder,ZCloud-Firstserver/boulder,lucasallan/boulder,sophie-h/boulder,hlandauf/boulder,mehmooda/boulder,ZCloud-Firstserver/boulder,jcjones/boulder,lucasallan/boulder,mehmooda/boulder,benileo/boulder,r0ro/boulder,r0ro/boulder,jsha/boulder,jfrazelle/boulder,ibukanov/boulder,patf/boulder,patf/boulder,benileo/boulder,jsha/boulder,jsha/boulder,lucasallan/boulder,r0ro/boulder,hlandauf/boulder,jcjones/boulder,bmw/boulder,hlandauf/boulder,mehmooda/boulder,patf/boulder