Use relative paths and more portable commands

[Jacoby6000]

This is some prep-work that allows for more portable installations. This enables NixOS compatibility and a way for users to test things without messing with their existing rofi configurations.

• The setup.sh script is updated to support custom directories for installation location. The script will still default to the old behavior, but users can have more control over where things are installed if they'd like.
• To support custom install locations, scripts have stopped using absolute paths, instead resolving their own file path and then using relative paths from there. This should work on any system that has readlink -f support.
• Themes have also been updated to use relative paths for imports rather than absolute paths.
• To support read-only file-systems, users can now specify themes via the CLI. Examples below
  • applets/bin/appasroot.sh type-1/style-2.rasi
  • launchers/type-1/launcher.sh 4
  • powermenu/type-1/launcher.sh 3
• Env vars can be used to set certain commands in the apps applet
• uptime has multiple variations, some of which do not have a -p option. This implements a portable uptime in bash
• Still some more work to be done wrt portability for the audio commands and music player stuff.

[Jacoby6000]

Just realized I need to make some adjustments to the image urls in the rasi themes. The rest seems to work as expected