Ensure that every file in Spack has a license (#2659)

* Ensure that every package has a license

Also fixes URLs with http://http:// doubled.

This is a continuation of #2656.

* Add license to every file in Spack

* Make sure Todd is the author of all packages

* Fix flake8 tests

* Don't license external Sphinx docs

* Don't display licenses in tutorial example packages

Also fixes typos and converts command-line examples
from tcsh to bash, which is more common