added new metric "Change Cost" and a new visualization "DSM"

* The file "MANIFEST" was updated
* New dependency, Perl module "Graph::Writer::DSM"
* Prefer to inherit from t::Analizo::Test::Class instead Test::Class in
  the Unit tests
* Added 2 new sample projects under t/samples

The Debian package for "Graph::Writer::DSM" is ongoing, while it's not
ready you can download from the link above:

* http://analizo.org/pub/Development/ActionItem34/libgraph-writer-dsm-perl_0.004-1_all.deb

(http://analizo.org/Development/ActionItem34)
Do not add Graph to cache, build Graph when needed

also, fix mispelling on "analizo_steps.rb"
removing the usage of 'shift'

also:
* explicit variable name in the 'foreach' loop
* s/add_vertices/add_vertex/
Merge pull request #30 from joenio/master

added new metric "Change Cost" and a new visualization "DSM"