Better error management in people DAO and REST API.

PeopleDAO functions now throw an IllegalArgumentException when an
invalid id or a null name or surname are provided. People's REST API
modified to return a "Bad Request" status when an
IllegalArgumentException is catched.
Tests for people management functionality added.

DAO class modified to support and alternative JNDI for the data source
through the "db.jndi" system property. A new testing database resource
was added to the Context.xml file.

DAO tests use the "spring-test" library to create a JNDI context, as
JUnit doesn't create any context. Additionaly, a custom DataSource is
created using the "commons-dbcp" library and injected into the context.
Testing database creation scripts are provided in the mysql-tests.sql
file.

REST API is tested in the server side using the
"jersey-test-framework-provider-grizzly2" library. These tests also use
the "spring-test" and "commons-dbcp" libraries to create a context and
inject a custom data source.

REST API is tested in the client side using the "Selenium IDE" and
"RESTClient" plugins for Firefox. Manual database reset is required
before launching the test suite.

Web interface is tested using the "Selenium IDE" plugin for Firefox and
using the "Selenium WebDrive" in JUnit tests. Same tests are implemented
in both cases. Selenium IDE tests require a manual database reset before
launching the test suite. JUnit test require the server to be started
using the testing database.