Revamp the shell prompt (somewhat)

New stuff:
- Path substitution for virtual environments
- Hide hostname if not running over SSH
Temporarily disable the current venv segment, and only do path substitution

Need to tweak it so that it will only appear when not in any child directories of the virtual environment.

Also, some color tweaks to make it stand somewhat out.
minecraft.sh: Update the launcher DL URL, it seems to have changed.

Also, new launcher \o/