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

https://issues.apache.org/jira/browse/CB-6481

Added the following changes and new features
* Hooks can be defined in .cordova/hooks/hook_type, hooks/hook_type directories, **config.xml** (by application developers) and plugins/.../**plugin.xml** (by plugins developers) 
* Javascript hooks retrieved from config.xml and plugins/.../plugin.xml will be run via new module loader with special **Context argument** passed. This object represents current hook script execution context including hook type, cordova version, paths, plugin info and other special utility modules.
* Introduced **before_plugin_install**, **after_plugin_install** and **before_plugin_uninstall** hooks.

See updated docs for more details:
https://github.com/MSOpenTech/cordova-lib/blob/CB-6481-hooks/cordova-lib/templates/hooks-README.md