Extract tests from the core and update symfony components

	As now the 'tests' directory is used, i think it could be a good idea
	to move the phpunit tests into that directory too.
	Moreover, this updates symfony components from 2.3.* to 2.3.21, 2.5.3 to 2.5.6
	and PHPUnit from 4.1.3 to 4.1.6