Add formats from spec to string type

[noha]

The following is the list of formats specified in the JSON Schema specification.

"date-time": Date representation, as defined by RFC 3339, section 5.6. "email": Internet email address, see RFC 5322, section 3.4.1. "hostname": Internet host name, see RFC 1034, section 3.1. "ipv4": IPv4 address, according to dotted-quad ABNF syntax as defined in RFC 2673, section 3.2. "ipv6": IPv6 address, as defined in RFC 2373, section 2.2. "uri": A universal resource identifier (URI), according to RFC3986. "uri-reference": New in draft 6 A URI Reference (either a URI or a relative-reference), according to RFC3986, section 4.1. "json-pointer": New in draft 6 A JSON Pointer, according to RFC6901. There is more discussion on the use of JSON Pointer within JSON Schema in Structuring a complex schema. Note that this should be used only when the entire string contains only JSON Pointer content, e.g. /foo/bar. JSON Pointer URI fragments, e.g. #/foo/bar/ should use "uri" or "uri-reference". "uri-template": New in draft 6 A URI Template (of any level) according to RFC6570. If you don’t already know what a URI Template is, you probably don’t need this value.