[WIP] Basic File Configuration

[dgduncan]

File Based Configuration

Add basic file based configuration along with the boilerplate to add future methods of configuration (config server anybody?) This included the following enhancements:

• "Smart Defaults" (TM)
• Allow-All hook
• TCP
• Websocket
• Stats

@mochi-co As part of this PR, I would also like to update the Docker README with some configuration instructions along with ways mount files. Is DockerHub parsing the README or is it currently set to manual and thusly must be updated on DockerHub?

@mochi-co @werbenhu @thedevop With this change, I updated how defaults for the server are set. Previously, when any Capability would be defined, the default values were not used. Instead, the server would use the defined Capabilities as prescribed and use the zero values of everything not explicitly defined. This caused things such as MaximumMessageExpiryInterval and ReceiveMaximum to be set to 0 instead of their defaults for example. This change to properly use the default makes sense to me; however, I want to make sure this change makes sense as per the MQTT spec. This change breaks two tests and I do not want to go changing how those tests work until I know this change makes sense as per the spec and is wanted by other maintainers.