learn how to prepare testing data

[xulabs]

@xiangruz please guide @wendingp

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basic steps:

1. particle picking
   https://github.com/xulabs/aitom/blob/master/tutorials/008_particle_picking.py

2. autoencoder
   https://github.com/xulabs/aitom/blob/master/tutorials/006_autoencoder.py

3. template search
   need to prepare a tutorial for this part
   related issue #14

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As an exercise, see if you can process the following tomogram

https://github.com/xulabs/aitom/blob/master/tutorials/000_general.md

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Then try the public data of the following paper

Routine single-particle CryoEM sample and grid characterization by tomography

The tomograms are separated in multiple empiar engries. Following is one of examples:
https://www.ebi.ac.uk/pdbe/emdb/empiar/entry/10143/