Generate enum-typed setters and constructors for signals with value descriptions

[felixvanoost]

• Updates the generated new() constructors and set_<signal>() setters to accept enums for signals that have an associated enum type (value description in the DBC).
• Generates additional set_<signal>_raw() setters for signals that have an associated enum type, which matches the existing behaviour of set_<signal> before these changes. This now makes the API for the getters and setters symmetrical.
• Cleans up the formatting of some generated getter/setter function comments for readability and consistency.

This is a breaking change for DBCs that have signals with value descriptions, but should make these signals much cleaner to handle. The best approach is to directly pass the enum-typed signals into set_<signal>, but you can retain the existing behaviour by simply using set_<signal>_raw instead.

This PR should be stacked on top of #176.