Added error management

[Cadichon]

Added an option (throwErrorOnUndefined);
Added data check;

When throwErrorOnUndefined = true, carbone will throw error on unvalid or undefine data.
Example :
data = { } and xml = {d.name} <\xml>
will throw "Error: data.name is undefined"

[dgrelaud]

Hello Léo !
I close the pull request.
We have a better solution for v2.1 ;)

[ilandblack]

Hi.
I can't find any error handling about missing fields in current version. Is there any?