[Feature] Add commands to backup and restore path

[HorridModz]

Backup user / system PATH variables to a separate environmental variable / registry key (PATH Backup) with commands path backup <!system or leave blank> and path restore <!system or leave blank>. The order of all 6 commands should be "add", "remove", "list", "get", "backup", "restore". Though the original 4 are in alphabetical order, to preserve this order with the 2 new commands, will have to assign each command a score: add will be 1, backup will be 5, etc. from 1-6.