Support multiple PHPUnit test suites

[rjkip]

• Ask whether the user wants to configure multiple test suites
• Then ask the test suite name, and the directory, repeat while the user wants to add more test suites.

Configuration example:

<testsuites>	
    <testsuite name="unit">		
        <directory>tests/unit</directory>
    </testsuite>		
    <testsuite name="integration">		
        <directory>tests/integration</directory>		
    </testsuite>		
    <testsuite name="system">		
        <directory>tests/system</directory>		
    </testsuite>		          
</testsuites>