Expandable hierarchical ports

[Nic30]

Currently hierarchical ports are collapsed to the most compact format. However the developer usually wants to see all signals in the interface (which is used in the port)

In order to support this we need to store this information in the json and we need to implement the onclick on the port which will perform the expansion/collapse.

[Nic30]

Example of treelist in d3.js http://bl.ocks.org/thehogfather/0e48ec486abbd5be17d7 @xkotek07 maybe we need something similar.

[Nic30]

We may also want to add help lines to visualize hierarchy more explicitly as hierarchy can be quite deep.

[Nic30]

After this issue is solved the json will contain also ports which are collapsed by default Nic30/hwtGraph#1