Add a reader for MAGIC data

[astrojarred]

Description
As mentioned in #836, the MAGIC Telescopes already have a detector class in graphnet.

This second MAGIC-related issue is a much larger task: add the MAGIC reader class and the necessary pieces to support it. I have a preliminary one working so just need to get it all cleaned up and into a PR.

Requirements

• Add a MAGICParquetReader class which can read the parquet files produced by the MAGIC analysis pipeline.
• Add two custom extractors which can extract the important information from MC and real data, respectively. The two have slightly different data formats/requirements so need to be implemented separately.
• Add an optional cleaning (data reduction) algorithm to the extractor. Due to the massive size of raw MAGIC events, it will be useful to add a basic cleaning algorithm into the extractor and allow for others to be tested and added later.
• Add a file containing the geometry of the camera, needed for some pre-processing or data-reduction algorithms (eg calculating neighbors)
• Ensure the already-implemented detector class works with the reader
• Add a small data sample for testing

If I am missing something else important here do let me know!