Allow passing backup etc. dirs on the command-line

[ISSOtm]

Currently, hUGETracker requires the directory it's in to be writable by whoever is running the program, for example to write backup files. This is okay if running hUGETracker "portably" (which is fine on Windows due to the pre-built distribution), but less so if doing a system-wide install (more typical on Linux via package managers).

The current packaging scheme I have is to put everything in /opt, and add a simple shell script in /usr/bin to run hUGETracker; it would pass the relevant CLI args to specify the user backup dir.