ADT Tutorial for Dev Site

Hey Jim,

I ended up not using the bare-bones `event-listing-portlet` due to the ADT implementation requiring multiple implementations of other future tutorials. In particular, the ADT exercise requires the *Configuration* menu, which will probably end up being a tutorial on its own. It also requires permissioning using the the `resource-actions` folder, which is a project in itself. Lastly, since we show the *Quick List* ADT editing the Locations Listing results table, we need the finished, working portlet to show the difference when using a custom ADT.

Therefore, the `begin` portlet is the `end` portlet with the ADT implementation removed. This provides what we need to begin, and allows us to focus exclusively on the ADT implementation. Let me know what you think.

https://issues.liferay.com/browse/LRDOCS-1000