Basic camera simulation

[viljarjf]

Start work towards #104

Simple implementation of crystals dispersed on a grid. Tested a lot manually, by moving around on the simulated TEM, but the automatic tests are not too expansive.
Example image and corresponding diffraction pattern:

And zoomed in to a single crystal:

With this crystal:

There is a lot to do still, as evidenced by the many TODO-comments everywhere, but this is a start at least.

I'll do a follow-up PR with small refactoring for the simulation-TEM and camera to use this new simulation. I left them untouched in this PR to reduce the scope. At the moment, to know the microscope parameters, the camera keeps track of the TEM instance in the same way that the TEMControl object does. Kind of hacky, I like the suggested implementation in #104 (comment) better.

[stefsmeets]

Nice work, looks good to me. Played around a bit myself and works as advertised 😁

My main problem with the code is the circular dependency (camera->ctrl->camera). I'm happy if this is fixed in a follow-up PR.