Improved generated comments

[mannprerak2]

closes #16

• Added comments option to config, Possible options are - {full, brief, none}
• Extracting comments for enum values, struct members
• Wrap brief comments (see clang_bindings.dart)
• Removed comment markups from full comments (see libclang-example/generated_bindings.dart)

[mannprerak2]

There's an issue with libclang's comment generation.
If an enum value has no comment, the comment of the enum value declaration above it is returned.
See this.
We can give an option to disable comment extraction for enum values.

[dcharkes]

If an enum value has no comment, the comment of the enum value declaration above it is returned.

Please open an issue on the clang issue tracker.

Possible workarounds:

1. Assuming the AST-visitor visits the enum values in order, we can detect whether it's exactly the same comment? Assuming we can detect whether the comment is from the same source lines: If it's the same source position we can omit the duplicates.
2. If we don't have the source positions, we cannot detect whether it's a literal duplicate comment in the source or not. We could make a setting whether to omit duplicate comments, and emit a warning. Or even make a setting whether to omit duplicates. But it feels very much like a clang workaround. (Unless it's intended clang behavior.)

If we're in case 2, maybe just leave it as is + open an issue here + link to the clang issue.