Add data processing test to CI

Setup tests for CI to include:

Checking elastic peak reconstruction.
Elastic yields
...

We need to setup a standard set of raw data files (outside of the repository) which can be downloaded and processed

To start we should get a list of recent elastic runs
Write a simple script to select elastics
Plot vs theta and find the peak.
Check that the angle matches the expected angle (within tolerances)
Do the same for momentum.