Python dependecy refactoring
Updated module to add pending modifications for python dependencies handling

- download command: now the full path must be specified.
- extract_archive : the full path is specified and the exec is run if it's notified.
- init            : commented optional packages
- python.pp       : windows_path dependency, pywin32 postscript refreshonly, pips case.
- python_dependend: refactoring to make the calls idempotents.
More refactoring for the python dependencies and some cleaning

- python class refactoring:
    - python\install.pp    -> installs python, pip and ez + path configuration
    - python\dependency.pp -> abstraction for python dependency.
    - nova_dependencies.pp -> refactoring and resources ordering
- extract_file command extracted to independent file in base/extract_file.pp
    - Contains 7zip installation
- download command now extracted to independent file in base/remote_file.pp
- commands.pp deleted, al relevant commands are now independent defines.
- init.pp: cleaning and referencing new nova_dependencies.
- removed some tools references: 7z (in extract now), gchrome, notpad, vcpp, vexa.
7zip now integrated in extract_file
Merge pull request #17 from luisfdez/feature/python-dependencies

Python dependecy refactoring