ability for plugins to be activatable. True by default, but plugin can be non-activatable is a dep is missing for example.

tryin to unpickle a GNU dbm file doesn't produce the same exception as bsddb. Handle both. Fixes #7013

Also use sed to remove now unneeded Vim lines, 2to3 -f ws_comma to fix
some whitespace, and fix some other madness manually.

Three core (raw) events (iq, message, presence) go also through Network Events Controller (layer between network library and Global Events Dispatcher, newly added) and from there they are dispatched through Global Events Dispatcher.
Ability to register new incoming network events (based on exisiting one) added. Modify-only network events are possible (eg. add some text each message, but don't create any new global event). Events creation can be chained.
Examples of new network events classes are in New Events Example plugin.
Events from src/gajim.py now all go through Global Events Dispatcher and only through it (easy to modify, in chain, data passed with them).

Events previously generated for D-Bus support in remote_control.py go through Global Events Dispatcher now - this means any plugin can subscribe to them.
Implemented D-Bus support plugin based on remote_control.py.

Improvements to GUI extension points handling - added method to remove these from PluginManager (memory optimization).

Removed logging from most of the code.

Length Notifier Plugin has configuration dialog (added entry with JIDs to be included when plugin is working) - fully usable.

Default values of configuration key has been added to GajimPlugin.

Some other minor changes/fixes.

Added GajimPluginConfigDialog class - dialog that plugins should use to present configuration to user.
Now, 'Configure' button is invoked only for plug-ins that have config_dialog.

Added new 'init' method to Plugin class that plugins can implement to make actions that need to be done only once - when plugin is added (not activated) to Gajim. In this method plugins should declare handlers for GUI extension points. This was created so that __init__ method doesn't have to be reimplemented in specific way (create config, load config) - it is all done by __init__ in Plugin class. If  __init__ is reimplemented, it must call Plugin __init__ (eg. using super() ) to plugin work properly.

Example plug-ins were modified to use init() instead of __init__().

Added new category in configuration - 'plugins'. It only holds one option for each plugin - 'active', which determines whether plugin should be activated on startup.

Now, Gajim remembers which plugins are active on exit, and activates them on next startup.

Plugin can be a package (directory) now. Added example plugin that modifies roster window (with glade file).

Added activate and deactivate methods to Plugin (used in forementioned RosterButtonsPlugin).

Added first version of 'Plugins' window. It's accessible through 'Edit/Plugins' item in roster menu. It seems that you can successfully (de)activate plug-ins through GUI now.

Added 'homepage' attribute to Plugin class.

Added (commented out) calls of pycallgraph in src/gajim.py for later use.

[xbright] Changed 'python' to 'python2.5' because code uses modules not available in previous versions of Python.

Added docstrings in reST format (also with todos). Commented out 'print' statements related to roster window. A few modifications to make code prettier (PyLint driven).

- basic PluginManager class that loads plugins from *.py files
  in given directories
- Singleton metaclass was created to use with PluginManager;
  notice: __init__ of class is called only once (not like in code
	that is included in Python Cookbook)
- variable to keep paths of plugin directories has been created
  (common.gajim.PLUGINS_DIRS); also added initilization of these
  paths to common.ConfigPaths
- added global variable with PluginManager object:
  common.gajim.plugin_manager
- created customized logger for plugin system ('gajim.plugin_system')
- created function decorator plugins.helpers.log_calls which logs
  each call of function/method; it also logs when function is left
- base class Plugin for plug-in implementation added; not much
  here - only empty class attributes: name, short_name, authors,
	version, description
- based on Plugin class, first plugin was created named
  LengthNotifierPlugin; it is used to notify users when they
  exceed given length of message during writing it (text entry
  field highlights)
- first GUI extension points works when ChatControl object
  is created (it is used in mentioned plugin)
- added 'epydoc.conf' file customized a little bit (file
	is also in trunk now)
- fixed indentation in common.sleepy module (also in trunk
	now)