[resource-query] Incorporate @morrone's suggestions

[dongahn]

There are a few nice suggestions made as part of #283, which I've never gotten around to address.

Create this ticket to track them:

1. scoring API class: Since this class takes several pages of screen space, only declare the functions in the class definition, and use external method definitions.

2. Use C++ type aliases instead of typedef

3. Move some of the classes that don't have to be a header file only solution to their own source files for better readability (e.g., class color_t).