[updater] updated plugin version (0.2)

- major code cleanup and fixes
- replaced xml.etree.ElementTree with xml.dom.minidom and created custom pretty xml function: _prettyxml()
- added ApiError class: handle api connection exceptions
- added _cleanpath() method: cleanup download/install directory from previous plugin install
- added plugin game filter: will retrieve from the api only plugins compatible with the running parser
- added upgrade method: upgrade a plugin if a new version is available
- added status method: get or set the status of a plugin