bcfg2-crypt: prevent traceback for certain decrypt failures
bcfg2-report-collector: use separate sysconfig file from bcfg2-server
Yum: better errors when yum helper output isn't valid JSON
MultiprocessingCore: greatly simplified parent-child RPC, removed non-thread-safe bits
Core: track statistics on resolve_client
Multiprocessing: proxy RecvProbeData calls

This proxies RecvProbeData calls to child cores to expire the probe
cache.  The probe data itself is not relayed, just the fact that there
was probe data received from a given client.

Fixes #129.