Syntax sugar for most common routing/selecting logic

[emil14]

We have some ideas for how to make nevalang programs more readable with #719 #721 and #722 but that's not everything that programming language usually helps with through interface of so called "operators". These are left:

Routers:

• If
• Cond (WIP)
• Switch

Selectors:

• Ternary
• Match
• Select

[emil14]

1. We don't talk here about for look (we have ForEach HoC but Early return from iterators is not supported #711 and it's not that powerful on context of scope capturing (we don't have closures))
2. Existing syntax (including deferred and chained connections as well as fan-in and fan-out) makes dataflow clear. Don't we damage dataflow readability by adding control-flow-ish (visually of course) statements? Is it still clear that instructions are not executed "from top to bottom" or the dataflow itself (where data comes from, how are connections formed)?

[emil14]

Close in favor of #802