Illustration of fine-grained logging control

[MatthewHambley]

This branch is not intended for immediate merger. Instead it illustrates a way of providing finer grained control over logging as discussed in #2.
It also limits changes to only the libraries logging object, not the root. I have not tested this to see if it works but it seems better from the point of view of not fiddling with things outside the library.

[coveralls]

Coverage increased (+0.4%) to 97.265% when pulling 3de7289 on MatthewHambley:LogControl into c357f6b on eerimoq:master.

[eerimoq]

In my use case I always want all logging from the entire program written to the log file and the console. Other than that I'm fine with the new function structure, but rename them to configure_console_logging() and configure_file_logging().