- removed plugin_util
- added key unbind feature
- updated plugin helper
- updated plugin helper - to have config as part of constructor
- updated MouseFreeURLHandler for plugin.py, unload
- removed circular dependency between plugin.py and config.py due to KeyBindUtil due to merging of plugin_util.py
2) plugin_util file to assist this and other plugins with key-press Helper function
3) adding Key Binding Help Functions in above (2) to config and preferences->keybinding to have a consistent behavior