Restructure shell launcher scripts to provide for invocation from any file system location or through symlinks

I hope I'm not being presumptuous, but being something of a terminal junkie, I saw a few ways in which your launcher scripts might be made a little more versatile. I've been a huge fan of the project for awhile and I thought that perhaps the best token of gratitude (besides a donation, but I did that some time ago) would be to roll up my sleeves and try to improve something.

-Peter