Minor: InchCoord initWithNSValue: to initWithNSNumber:

Originally, I wanted to support all NSValues equally (somehow).  Then I thought it made sense to have a “double value” vs. a “NS– value”.  While that does sort of make sense for a readonly property name (and since NSNumber is an NSValue subclass), it doesn't for a constructor that takes specifically an NSNumber.

• Constructor now named initWithNSNumber:, matching the format (the type name full-out) of initWithDouble:.