Extract interface arrays

[Nic30]

Extract interface arrays as separate library, because it is complicated and users does not understand the difference between

• an array of interfaces (= python list of Interface objects)
• an array interface (Interface object with multiplied width and overloaded indexing to allow index parts of this array).

It is useful feature but it is too complicated for base hwt library. Learning curve of uses and intuitive usage has priority.

This also means the removal of SimProxies for this interfaces. And magic indexation overriding, array items cache and it's usage for interfaces.

~ 2018-06-30

[Nic30]

done in e5cd87228596c689320df3e84e6bc2710151d077