Changing 'pixels' parameter in some 2D observers does not update image geometry.

[vsnever]

Setting pixels parameter in PinholeCamera and OrthographicCamera after initialisation must trigger a call to _update_image_geometry() just like in CCDArray. However, the default setter from the parent class is not overridden here, so the image geometry will not be updated.

Setting pixels parameter in VectorCamera must not be allowed at all. Now it is possible via the default setter from the parent class. It's unlikely that someone will try but maybe a warning should be raised if this happens?

@pixels.setter
def pixels(self, value):
    warnings.warn("Setting 'pixels' parameter is not allowed in VectorCamera")

[mattngc]

Thanks Vlad, good catch. Indeed, it is a bug.

[CnlPepper]

Curious, I thought I fixed that. I must have forgotten to merge it. The vector camera needs bit of tiding up, it was originally quickly cobbled together to address a specific use case.