This function returns the first available connection in the hashtable of connections
marked with a Boolean false and sets the connection to used with a Boolean true.
The SQLRequest class uses an instantiation of the ConnectionPool class
and uses connections from the ConnectionPool to create a Result set
based on a search query and return a Result Set
Handles the login verification, errors thrown during verification, and prints the frames
for the application or an message informing the user why the login failed.