Consider cleaning up signature formatting

[madelson]

I feel that the member signatures generated by the tool could be cleaned up a bit (e.g. in this file).

Primarily:

• It would be nice to use T? syntax rather than System.Nullable<T> for nullable value types
• It would be nice to have spacing around = for parameter default values
• It would be nice to use = default instead of = default(T) for value type default values

Thoughts? If you agree, I'd be happy to work on a PR.

[Doraku]

hum the definition of a member use ICSharpCode.Decompiler to be written, I am not sure this is something easily changeable. It should at least be easier to clean the System.Nullable<T> > T? in type links.