Add params to bad-type error in NumberValidator.

Previously, the parameters required by wikibase-validators-bad-type
were missing.

Change-Id: If59d84163f0de3dee9095100f401a2ce6227c8ac
Make DataFieldValidator require the field to be set.

DataFieldValidator should fail validation when the respective field
is not set (missing or null). Or current use of DataFieldValidator is
consistent with that assumption.

Previously, DataFieldValidator would fail hard if the field as unset,
and passed the value to the sub-validator if the field was null, which
was not consistent with the current usage.

Change-Id: I64c139c11f60b69f7a7a674bb95c87934ce58861
Merge "Add params to bad-type error in NumberValidator."
Merge "Make DataFieldValidator require the field to be set."