[2.2] add support for optional custom error message for Configura...

RFC: ref #1666

Basically this is the start, but i wanted to ask which one of these options is better:

1. extend/override the base Exception class to include the custom error message
    this requires a modification of the throw specific expection passing Exception($this) meaning it is getting
    the current node or the node from which the exception is being thrown

2. propagate the changes in every class that throws exception similar than this PR
    this would require changes in every particular class

Please vote whether 1 or 2 is more fit

Thanks to all symfony2 community :D