Allow users to create their own Java Functions to be used via Android JavaScript Interface

Similar to how in the current Tasker JavaScript(let) actions, there are built in functions (http://tasker.dinglisch.net/userguide/en/javascript.html)

This idea would basically expand on that and allow you to create your own built in functions that can better handle the Android side of things when writing JavaScript. 

See original posting of the idea here on reddit (https://www.reddit.com/r/androidapps/comments/5ag991/request_tasker_plugin_to_add_custom_java/)