Added "swmod adddeps"
Removed "default" module.

* Having a "default" module was a bad idea - software is often installed
  into "default" by accident.
Make swmod compatible with plain sh
Replaced use of "==" equality test by "=" in hostspec
Changed Linux distribution tag from slc to scientific for non-CERN slc
Added support for lib directories named "lib64"
Fixed MANPATH
Updated copyright information
Updated README and renamed it to README.md
Reformatted swmod usage output