Change license to BSD 3-Clause License

The package namespaces CAL, DJO, PMA, TFL, and TGL are changed from the
GNU Library/Lesser General Public License to the BSD 3-clause license.

The package namespaces ATAX, GTW, JNJ, LNX, MOM, and ReST are changed
from the GNU Affero General Public License to the BSD 3-clause license.

Add rewrite_license_header.py to change the license notices in the
header comments of source files. Due to hysterical raisins,
`rewrite_license_header` needs a lot of special casing. In general, I
used it like this::

    python rewrite_license_header.py $(git grep -l 'MIT License or')

    python rewrite_license_header.py $(git grep -l 'GNU General ')