Improved Login Page

Implemented the following features: Inputs fields properly sanitized,
Anti-Brute force mechanism (locks account for 20 minutes after 5
attempts), overall cleaner code, Error messages display when erroneous
log-in input encountered, also included a .htaccess to prevent directory
browsing.... The "header" bug seen in the previous
revision has been fixed. The 'How to set up the database" file has been
updated accordingly. I also edited the file hierarchy for optimal file
navigation.