Removed whitespace and added dtools/bin/remove-whitespace as a tool to do this in the future.

The sed script was provided by Moritz Fischer.

Refactor gr-howto-write-a-block such that it no longer installs into
the gnuradio python namespace, but rather in the howto namespace.

This allows it to be installed under a separate --prefix in the common
case where the user doing the "out of tree build" is going to be...