IIR EQ base class

This introduces a common base class for all fidlib based Filters.
It makes use of templates to be generic as possible, without introducing CPU overhead. 
I have nothing found in the Google style guide, But here http://www.cplusplus.com/doc/oldtutorial/templates/ all Template "Macros" are capitalized so I did just the same. 
IMHO we should keep the distinguishing between a  kSize, a normal const and SIZE, a template object?
Do you agree?