Update the way how we render long signatures

[romanowski]

Our current UI renders all modifiers as well as full signature what may whole thing very long. It is getting even worse by the fact that we align names what leads to often uoccupied space.

We shoudl either adopt scaladoc approach (render full signature on hover) or find a clever css that allows us to render full signature in most cases and somehow wrap it in cases when it it is getting too long

[romanowski]

Some ideas:

• hide packages in private[x] modifiers as well as annotations
• add a clear indication that signature is not complete

[romanowski]

cc @TheElectronWill @abgruszecki