Update core.shl

Added options to bytes_to_hr(), and hr_to_bytes() to handle SI digits, and various output options. human_readable() does not support similar options, and there are no plans to add them at this time. Fixed minor issue in min().

Cleaned up a few comments in format.shl.

Added disk.shl to tracking, but it is not in a working state, and I don't expect work to continue any time soon.