Improve Non-interactive use of script

[stablestud]

This commit improves Gogh security and usage when being used non-interactively (for usage with scripts)

It includes not only one but multiple improvements:

• Close potential backdoor by removing downloading of files from remote servers
  • Instead files must be downloaded manually beforehand when using theme shell scripts directly
  • gogh.sh is unaffected, it will download the files
• Remove hardcoded path for apply scripts in theme shell scripts (was parent dir)
  • Instead the path to the apply scripts can be set by following environmental variables
    • GOGH_APPLY_SCRIPT
    • GOGH_TERMINATOR_SCRIPT
    • GOGH_ALACRITTY_SCRIPT
  • Fallback to old behavior if no path was given
• Add missing Python requirement for Terminator script
• Add additional .gitignore files to cover Vim swap files and Python virtual environment

I could split up the commit into 3 smaller ones, but the GOGH_* environment feature and removal of file downloading is closely coupled and therefore cannot be split up into smaller commits.

[stablestud]

I fixed a bug in the theme shell scripts, therefore I had to update the commit. Should be all set now :)

[Mgldvd]

Thank you!