More documented examples

[PierreRaybaut]

A lot of features have been added recently and should be documented to be maintained properly in the future.

The minimum should be to explain in a line comment the purpose of each line in the examples. But, now that formlayout (or should I write QuickForm) has a lot of features, without a decent documentation, maintaining the library could be difficult for people other than you: that is a real threat for the library sustainability.