Improved plugin system:

- the user is asked at start wether to load or deny unregistered plugins, but can make it mind later in config->plugins
- added API and SVN numbers into required external plugin symbols
- user-defined plugin rules are dropped when a plugin changes (hash changes) or when the main executable changes.
- added new status flags (Plugin denied, missing API/SVN numbers)
- modified saveList()/loadList() to allow saving a list of rejected plugins as well.
- added methods in notifyBase and inherited classes to ask for plugin confirmation.

- adapted VOIP plugin to follow these new rules (API+SVN numbers). Other plugins should be adapted as well by addign the 
 missing symbols (RETROSHARE_PLUGIN_api and RETROSHARE_PLUGIN_revision).



git-svn-id: http://svn.code.sf.net/p/retroshare/code/trunk@5529 b45a01b8-16f6-495d-af2f-9b41ad6348cc

libretroshare/src/retroshare/rsiface.h

@@ -206,6 +206,7 @@ class NotifyBase
 	virtual void notifyHistoryChanged(uint32_t /* msgId */, int /* type */) {}
 
 	virtual bool askForPassword(const std::string& /* key_details */, bool /* prev_is_bad */, std::string& /* password */ ) { return false ;}
+	virtual bool askForPluginConfirmation(const std::string& /* plugin_filename */, const std::string& /* plugin_file_hash */) { return false ;}
 };
 
 const int NOTIFY_LIST_NEIGHBOURS             = 1;