Provide a logging configuration file loading mechanism

[ehclark]

Is your feature request related to a problem? Please describe.
It is difficult to dial up and down the log level for AnyVar and its various components without updating the code to do so.

Describe the solution you'd like
The administrator should be able to provide, at runtime, a YAML file to configuration the Python logging module. If the ANYVAR_LOGGING_CONFIG environment is specified and points to a file, the file is used as a logging configuration file to configure the logging module when AnyVar starts up.