JController::factory() and createEnvironmentArray() as discussed in joomla-dev-cms group

Added to JController the following methods:

1) factory()
2) createEnvironmentArray()
3) setTask($task)

Changed execute($task) that if no task is passed, it executes the
$this->task (which is set also by the factory method)

See discussion https://groups.google.com/forum/?fromgroups#!topic/joomla-dev-cms/7tjVkzc08Ks (Object oriented components , any plan?)

2012-04-19 by Duccio Gasparri <duccio.gasparri@gmail.com>
Change-Id: I2a4ded062856670e364128f3cb74716b84b23eea