Save Steam web API spec in repository

[fizzy123]

This change saves the Steam web API spec in a module in the steamapi. This means that people don't need to make a call every time they want the Steam web API to be populated in Steam Interface, and also means that there is now a file that people can look at to see what functions are currently supported and what parameters they accept.

Down the line, it would probably be nice to format the spec better so that it actually defines python classes. This would be more readable and mean that the python functions are better defined.

Additionally, I modified the APIResponse.dict function to recursively convert all APIResponses to dicts, rather than only convert the top level of the APIResponse into a dict.