Default skill and intent handling

I have tweaked the default handling of intents a bit:

As a smaller change, Peeqo looks up the responseText from Dialogflow (or the response from any other intent engine) or the intent name on Giphy if no intent has been defined in dialogflow-intents.js. While playing with Peeqo this has been one of the most important changes I've made so far because it allows me to add many new intents on Dialogflow without having to touch Peeqo's code.

I also propose a new skill structure which allows to add new intents in a more modular way without having to change dialogflow-intents.js. This makes it easier to fetch future updates from the Git rep without having to re-write existing skills/intents. It should also allow people to add new intents or skills which are compatible with future intent engines. Furthermore, it would be easier to download standalone skills or intents and simply copy them into one directory without having to touch any other code.

As a demo I have added a new datetime skill which displays the current date and time.

I managed to comment with my work account instead of my personal.