[RFC] Formalize support for IP-XACT

IP-XACT is a xml metadata format for describing interaces to IP circuit designs.

## Motivation
There is a lot of interest from CAD vendors for us to support IP-XACT to streamline integration with their tools. A lot of work has been done here, particularly with respect to the Craft 2 project. It is not clear that this code has been kept current, or was ever adequately documented.

## Current state
IP-XACT implementations exist in
- [rocket-dsp-utils](https://github.com/ucb-art/rocket-dsp-utils/blob/master/src/main/scala/ipxact/IPXact.scala)
- [rocket-dsp-utils](https://github.com/ucb-art/rocket-dsp-utils/blob/diplomacyPort/src/main/scala/dspblocks/IPXact.scala) and again here, with diplomacy support.
- There has also been work done by Intel [Reference Needed]()

## Impact
This should be minimal disruptive because it does not alter existing API's. There are several
steps to solidify support
- Identify the right repository for it to live in.
- Test existing code and modernize as necessary
- Provide more Documentation