Adding the mapped type to the form type references
Merge branch 'issue1387_2.1' of github.com:Sgoettschkes/symfony-docs into Sgoettschkes-issue1387_2.1

Conflicts:
	reference/forms/types/birthday.rst
	reference/forms/types/country.rst
	reference/forms/types/hidden.rst
	reference/forms/types/language.rst
	reference/forms/types/locale.rst
	reference/forms/types/repeated.rst