stddoclet: Need to document properties apart from their getter/setters

Categories are needed for properties.

Ex: setColor(), getColor() methods define the property "Color".
It is the Color property that needs explanation, not the individual methods.

   PROPERTY
      getProperty
      setProperty
      isProperty
Sometimes other collections of methods belong together in a single
category, as well.

Might be handled like categories for static fields (bug 4085608)