Singleton instance attribute is now private (use call to get it)
Add PluginManager
Add plugin manager tests and fix some bugs
Test plugin proxies and adding plugin dynamically
Remove extraplugins, add doc
Add debug classes
Fix logger syntax error
Fix bug when pluginmanger debug mode == 'loading'
Split PluginManager in two parts:
  - PluginManager
  - PluginInstanceManager (temporary class, must be improved)
Plugin Instance are now managed using services
Add missing plugin service module.
proxy_class parameter is renamed to plugin_proxy
Merge pull request #88 from gbaty/plugin_manager

Plugin manager