'Returns a boolean representing if this plugin is enabled.
If ``project`` is passed, it will limit the scope to that project.
>>> plugin.is_enabled()'

def is_enabled(self, project=None):

    if (not self.enabled):
        return False
    if (not self.can_disable):
        return True
    if project:
        project_enabled = self.get_option('enabled', project)
        if (project_enabled is not None):
            return project_enabled
        else:
            return self.project_default_enabled
    return True
