File access rework

[Querz]

This is a complete rework of the pipeline that loads files, processes them and then saves the result to disk with an aim for abstraction so this can be used for everything that loads, processes and saves files.

Explanation

There is a "MCAFilePipe" class now that runs 3 ThreadPoolExecutors:

• One is for loading files in order, because loading files in order is faster than loading a lot of files at the same time (at least for HDDs).
• The second one is for processing the loaded data on as many Threads as Runtime.getRuntime().availableProcessors() returns.
• The third one is for saving the resulting data. This usually happens in 1-4 Threads.

A custom workflow for loading, processing and saving can be implemented by extending LoadDataJob, ProcessDataJob and SaveDataJob, see for example RegionImageGenerator.