Improve formatting and fix validation of input elements

Glue the * to required field labels.
Don't use class attribute for validation. Use
data-rule-[date|datetime|url|number] and required attributes instead.
Fixes #1822
Put hidden input fields below the controls they're linked to so that the
validation messages appear below the controls.
Change input type of EMAIL fields to "email".
Merge pull request #1821 from erwinwinder/master

Refactor importer
Merge branch 'master' of https://github.com/molgenis/molgenis

Conflicts:
	molgenis-core-ui/src/main/resources/templates/molgenis-input-elements.ftl
Merge pull request #1823 from fdlk/master

Improve formatting and fix validation of input elements
Added dependency resolving for self references