Added function wassup_install

[admin]

Helene added a new function, "wassup_install()", that creates/updates the database and sets default options upon Wassup activation, and added an activation hook to execute the function. Also removed the now unnecessary create/update commands from both "wassupAppend()" and "Wassup()". This improves Wassup's efficiency by reducing the number of database queries/updates on every hit. This also means that Wassup must be deactivated before every upgrade so that "updateTable" will run when the new version is activated. Wassup upgrade instructions may need to explicitly state this even though deactivation/reactivation is the standard way to upgrade a plugin in Wordpress.