Number fields reject invalid values before saving

A Number property is now edited with an HTML5 number input, so the browser rejects letters and, for the integer and long types, decimal values before the form is submitted. A value outside the integer range is refused the same way, and a value outside the long range is now reported with a readable message on save instead of a server error.

The "Size" property metadata no longer applies to a Number field: the attribute it used to set is ignored on a number input, so it is no longer emitted.