Centralize __repr__ and __str__ in base Region class

[larrybradley]

The PR also defines separate __repr__ and __str__.

Example:

>>> from regions import PixCoord, EllipsePixelRegion
>>> cen  = PixCoord(10, 20)
>>> reg = EllipsePixelRegion(cen, major=5., minor=3., angle=45.)
>>> reg
<EllipsePixelRegion(PixCoord(x=10, y=20), major=5.0, minor=3.0, angle=45.0)>

>>> print(reg)
Region: EllipsePixelRegion
center: PixCoord(x=10, y=20)
major: 5.0
minor: 3.0
angle: 45.0

[cdeil]

This is great!
+1 to merge if tests pass.

The multi-line strings in the tests with the arbitrary wrapping aren't pleasant on the eyes. But I don't know a better way to do it, so unless someone else has an alternative, possibly nicer suggestion, no need to discuss that point.

[larrybradley]

@cdeil I think the only alternative is to leave them as single long (wrapped) lines.

[cdeil]

I think the only alternative is to leave them as single long (wrapped) lines.

Yes, that's what I've used before mostly. But now that I see how you've done it here, I think I prefer your solution. (no vertical scrolling while reading it)

[bsipocz]

Tests are passing, and as @cdeil has already approved above I'm merging.