Move debug, logs, and config files to consistent directory

[Kneelawk]

Currently, the application places debug files, logs, and config files in the current directory from which the application was run. This leads to a mess and can be unpredictable. It would make sense if these files were placed in a consistent directory, regardless of where the application is being run from. It might make sense to have this directory be ~/.fractal-rs-2 or equivalent.