Plugin system improvement needed

[CarolinaFernandez]

There are some issues that should be taken care of in the future as to improve its development:

• Settings are not loaded anymore in plugin.py because of the objects PLUGIN_LOADER and TOPOLOGY_GENERATOR, two classes instances persistent in memory that were assigned to those variables. This caused some interference with the authentication in auth.wsgi. To solve this, the settings are loaded now in the urls.py; but this is not a nice place to do such loading. Take a look at this to see how this can be put back into plugin.py

• Settings are now loaded twice: data in variables is repeated. See how to load only once

• Path for plugins is now hardcoded in settings.py) (some problems arose from setting this in the following old fashion, inside plugin.py):

  PLUGIN_LOADER.set_plugins_path(os.path.join(os.path.dirname(file), "../../../plugins/"))