Console help refactoring

Fixes #4535
It's returning null instead of the help info from PHPDoc. So within the action I'm calling `$action->description`, it will not give the expected result. 

It seems to me @cebe's original code is better. Although it has code redundancy, it can be optimized by extracting the PHPdoc parsing code into a helper class or something similar.

I also recommend this method naming: 

* `Action::getHelp()`: detailed help
* `Action::getHelpSummary()`: a one line help summary
* `Controller::getHelp()`: detailed help for the controller
* `Controller::getHelpSummary()`: a one line help summary for the controller
* `Controller::getActionHelp()`: detailed help for the specified action ID
* `Controller::getActionHelpSummary()`: a one line help summary for the specified action ID