In the process of adding in login functionality through Apache Shiro.

* Moved register.gwt.xml to resources/ folder.
* Modified pom.xml to include Shiro dependencies.
* Added LoginService/LoginServiceAsync
* Added LoginFailedException

NOTE: Login functionality is not working yet.
Added a LoginScreen class.
Working implementation of the login form.

Added in a form interface for logins. The EntryPoint for both the
registration and login forms will be the same. Changing between the
two will involve setting the correct Screen to the container. A few
changes have been made to support this.

* Renamed the RegisterPage class to ContentPage.
* Renamed the container id in register.html.

Login functionality will utilize the Apache Shiro framework for
authentication and jBCrypt for password hashing. As Shiro does
not have support for Bcrypt, I extended the CredentialsMatcher
interface to add support for Bcrypt.
Added verification functions for password, email and contact fields.
Merge pull request #5 from Ayrx/field-validators

Added verification functions for password, email and contact fields.
Merge pull request #6 from Ayrx/login

Login
Merge pull request #7 from Geraldlim91/master

Changed database used from MySQL to PostgreSQL. Made modifications to the registration page and corresponding database fields to reflect the needed information.
Modified database connection parameters
Refactored LoginScreen and RegisterScreen to use UiBinder