User can now logout

- Created Account/account_logout.php; unsets the 'firstName' Session
variable (would an Account class be useful?)
- Gave an ID to the 'Logout' link in header.php
- js/mylibs/lacy.lib.js now attaches an click event to the 'Logout' DOM
element; sends ajax request to Account/account_logout.php and then
refreshes the current page
Unset Account-related Session VARS

- Account/account_logout.php now unsets all SESSION variables that are
related to the account
Added Account classes
Updated Account class
Trying to make accounts work better