[SOBP1] [Database] <Stable> Deployment of JPA+Eclipselink with derby as Embedded (local resource) Database. 

 -  Basic user model as an Entity defined, id will be automatically generated; users will be referenced by email on the client-side.
 - DAO interface and specific DAO for user added as well,
 - Implemented a Database Handler Interface together with its implementation for ease of development and readability of code purpose,
 - Handler instantiated in runtime (see WriteCommand.java) and entire process is currently WORKING PROPERLY, storing users' information on a local test Database.
 - NOTE: Before building this project, your path must be properly set in src/conf/persistence.xml file (as javax.persistence.jdbc.url value).
 - NOTE: Remove folder "test" under ./databases directory and make sure that property "eclipselink.ddl-generation" is set to either "drop-and-create-tables" or "create-tables".
 - TODO: Check email verification on user add tasks (see TODOs in SOBUserDAO.java).
 - TODO: Look for indexation on users table by e-mail, since it will be our main identifier on LogIn tasks.
 - TODO: Add operations to UserDAO interface such as getUserByEmail, and implement the leftovers.