profile.py: Log # of queries loaded and raise an error if 0 are loaded

[tstromberg]

This adds some diagnostic log and error messages to profile.py so that people can debug why profile.py is quietly exiting. In my case, it was because I was passing an osquery pack file to --config.

Old Behavior

Invalid config:

$ ./profile.py --shell /usr/bin/osqueryi --config pack.conf

Notice the lack of any output or error code.

Valid config:

$ ./profile.py --shell /usr/bin/osqueryi --config osquery.conf
Profiling query: SELECT hostname, cpu_brand, physical_memory FROM system_info;

New Behavior

Invalid config:

$ ./profile.py --shell /usr/bin/osqueryi --config pack.conf                       pack.conf parsed as JSON, but does not contain a 'schedule' or 'packs' stanza. Is it really an osquery configuration file?

Valid config:

$ ./profile.py --shell /usr/bin/osqueryi --config osquery.conf
1 query loaded from /etc/osquery/osquery.conf

Profiling query: SELECT hostname, cpu_brand, physical_memory FROM system_info;