"Interface of component" is defined over expose and bindings, which is confusing

[linusha]

We once had the design goal of expose describing the whole interface of a component. "Interface" in this sense encapsulates two things in my opinion:

1. All functions that the model of a component brings that should be callable from the outside.
2. All functions that the model of a component changes, when compared to the implementation in the original morph class of the good old Morph or whatever the type of the component is.

I recently learned that this assumption was always broken, due to the override parameter of bindings. However, the implication of this really dawned on my only when merging #1593, where it is very obvious that there are now keybindings and commands that come from inside of the model without them being listed in exposed any more.

We briefly discussed two solutions, and I could live with both of them. However, they are also not mutually exclusive:

1. @merryman proposed to just get rid of the override option in bindings and move that over into expose.
2. An alternative approach could be to revisit the original goal I had in mind with the above concept of an "interface", which is mainly concerned with the affordance of reading code and using components. This could also be tackled by visually indicating methods that comprise the interface in a graphical way inside of the systems browser. This could for example be achieved with a different icon inside of the muller-columns or a colored icon.