WPDb module first huge update

A first round of updates to the WPDb module.

Users, options and posts

I will not go over the details but have refactored and added some of the methods related to CRUD operations with users and options in the WPDb wp-browser module but I've also began the implementation of the post handling operations.
I've reviewed and refactored the method to have a post in the database along with its meta and while that's just a first version I'm working toward a complete code coverage of the module to have a reliable base to iterate upon.

Read more in the README file.