Peakrdl-ipxact

**Updates**
Rework how importer maps IP-XACT names to SystemRDL type names. (11)
Prior behavior would be very prone to namespace collisions.
New behavior imports names as concatenated component/memoryMap names.
See docs for more details: https://peakrdl-ipxact.readthedocs.io/en/latest/importer.html

**Updates:**
* Discard enum members with duplicate values or member names.

**Updates:**
* Minor compatibility update to importer enum creation.

**Updates:**
* Add PeakRDL command line application entry point hook

**Updates:**
* Deprecating import via `peakrdl.ipxact` namespace package. See details here: https://github.com/SystemRDL/PeakRDL/issues/4

**Changes**:
* Rework how top-level elements are imported:
* Now, top-level memoryMap *and* the child addressBlock elements are always imported as addrmaps into the root namespace. This behavior offers more flexibility in how IP-XACT documents are used within a larger design.
* Behavior is more consistent and easier to understand.
* **NOTE**: In some cases, imported names may differ from what was done in v2.x.x. See new import naming behavior described here: https://peakrdl-ipxact.readthedocs.io/en/latest/importer.html
* Importer now can load multiple memoryMap elements from the same IP-XACT document (6)
* Improved documentation: https://peakrdl-ipxact.readthedocs.io