hash port, addressable port with string indexes

[forresto]

This would make it possible to specify names for the ports, as opposed to a numerical index. Otherwise, it would work the same as array ports.

noflo/noflo#262

[alfa256]

Iterating over connected hash ports would be a needed functionality, also some convention for hash port names.
I suggest sticking to lowercase and snake_case names for hashports.

[trustmaster]

This feature would improve readability and maintainability of static routing in FBP apps a lot.

Currently I have to write something like this:

'GET /index' -> PATTERN[0] Router
'GET /admin' -> PATTERN[1] Router

Router REQ[0] -> REQ IndexController
Router REQ[1] -> REQ AdminController

These numeric indexes are getting hard to maintain as the number of them grows. Compare it to this:

'GET /index' -> PATTERN[index] Router
'GET /admin' -> PATTERN[admin] Router

Router REQ[index] -> REQ IndexController
Router REQ[admin] -> REQ AdminController

Makes much more sense to a graph designer.