feature: setters for Shape.id and .name

[oscartprom]

[scanny]

Hi Oscar, these properties are common to all shapes, here they are in the docs :)
http://python-pptx.readthedocs.org/en/latest/api/shapes.html#shape-objects-in-general

[oscartprom]

Looking at the source code there seems to be no setter method, and I tried "shape.id(10)" and "shape.id = 10" but neither worked.

[scanny]

Ah, right, got it. I'll leave this issue open as a feature request to add setters for those two properties.

[scanny]

Shape.name setter added in latest commit on develop 9dc51fb; will be included in next release.

Adding a Shape.id setter was rejected after consideration. The shape id is inherently void of semantics, it is simply a unique identifier and is always provided by either PowerPoint or python-pptx. Adding a setter would invite using it to encode meaning and would add unwelcome complexity to internal processing to ensure the id remained unique. I suggest using Shape.name to attach meaningful information to a shape when desired.