[BUGFIX] GetByType always crashing

Accidentally left double quotes inside of the query() call which made GetQuery()'s parenthesis part of the query instead of method call.
[FEATURE] Added VerifyCredentials()

Added a new method called VerifyCredentials which queries the DB to check user supplied credentials. If credentials are verified, sets session variable "username" to the person's username and returns true, otherwise returns false. Throws exception or mysqli_sql_exception if failing to connect to DB/retrieve DB connection.
[FEATURE] Added generic functions for security

Added a new file, Security.php, which includes the XSRF class file as well as some generic functions for requiring pages to be served via SSL, ensuring that users are authenticated for given pages, and ensuring that a logged in user does not see the login page if they browse to it.