fix #617 InputValidationHandler issue

A javascript error was raised in the following use case:
inside a container having scrollbars, a field is in error,
the field is focused (so that the error tooltip is open),
scroll the container with the mouse wheel.
feat #500 utils.String.dashedToCamel|camelToDashed
fix #499 conform standards regarding dataset in Html.buildAttributeList

Added check for invalid keys passed to `dataset` in
utils.Html.buildAttributeList.

So far it only logs warning, to be switched in backward-incompatible
release.

Close #500.