Examples, preferably with data

[alisterburt]

ideally we want examples for the following

• Particles on tomogram
• Refinement results viewing
• Template matching results viewing
• Transformation block applied to chemoreceptor data (hexagon -> c2 axes)

[brisvag]

Importantly, we shouldn't clutter and weigh down the repo with heavy data. We should either host them on a separate repo that doesn't need frequent updates, or even better we should set up some script to download the necessary data from somewhere.