beginning to add l2norm to atoms

git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/mptk/trunk@2107 0f77665a-23fb-0310-bc23-e91fd8efc3e1
removed the l2norm to atoms

git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/mptk/trunk@2108 0f77665a-23fb-0310-bc23-e91fd8efc3e1
pyMPTK: improve error reporting, and get signal as doubles not floats
pyMPTK: write decay, even if not writing book
pyMPTK: improve error reporting; get signal as doubles not floats; write decay even if not writing book

git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/mptk/trunk@2109 0f77665a-23fb-0310-bc23-e91fd8efc3e1