Generic combinator like entity

[mrvn]

Every mod I've looked at that wants to generate signals uses a constant combinator as base entity. When you need multiple wire connections, for example when you have input and output signals then multiple entities are used. Which causes all kinds of problems and confusions. The arithmetic/decider combinators can't be repurposed because their functionality is hardcoded (e.g. you must specify icons for all the functions they have). Which causes all kinds of problems and confusions.

So my request is the following:

Have a generic combinator like entity with:
- list of wire connections (input, output separate?)
- animation when active
- event when signal inputs changes