Preset operators should avoid using `bpy.context.object.data` as a base
path to properties. This path is not available in the buttons context
when using pinned datablocks! Instead use the specific
`bpy.context.camera` and `bpy.context.lamp.sky` paths now, which lead to
the correct datablocks in any case.
- Added support of variable size sensor width and height.
- Added presets for most common cameras, also new presets can be defined by user.
- Added option to control which dimension (vertical or horizontal) of sensor
size defines FOV. Old behavior of automatic FOV calculation is also kept.
- Renderer, viewport, game engine and collada importer/exporter should
deal fine with this changes. Other exporters would be updated soon.
