CB-6481 Added unified hooks support for cordova app and plugins

* Hooks can be defined in .cordova/hooks/hook_type, hooks/hook_type directories, config.xml and plugins/.../plugin.xml
* Javascript hooks retrieved from config.xml and plugins/.../plugin.xml will be run via new module loader
* Introduced before_plugin_install, after_plugin_install and before_plugin_uninstall hooks
CB-6481 Updated hooks documentation