Creates way to change DB and Collection

These updates add a way to move across database and collections. 

I created three functions to do this: `showdbs`, `changeDb` and `changeCollection`.  `showdbs` is just an HTTP request to get the list of DBs the user is an approved contributor to.  `changeDbs` will change the subreddit the user is pointing at.  `changeCollection` will change the collection the user is pointed at.  

(#5)