Change default logging to disabled, custom options

Previously, the default logging state was all Errors, logged to file.
This has been changed so that logging is disabled by default (using
Analog's Null handler).

In addition, the Analog handler has been exposed through the settings, so
that a user may specify a custom handler (syslog, etc) instead of the
default file handler.

Closes #12
Merge branch 'develop'