Group operator trees by default

[Nic30]

Operator trees like (a) or (b) are commonly found in circuits. They usually form large node clouds which are just slowing down the rendering process and obfuscating the result. It would be better to group these trees under a single large node and expand them only if requested by user (on click in same way as other components).

The shape could have some mark to note if the expression tree hidden behind have some specific format (full tree, balanced tree, "sequence like", ...)