formats: consider add INTEGER_SCHEMA and FLOAT_SCHEMA

[Dentrax]

Description of issue or feature request:

It would be great if we have the INTEGER_SCHEMA and FLOAT_SCHEMA formats. We can use these schemas in order the validate whether the given content is in integer or float format.

Actually, there is already an Integer class in the schema file, we can easily use this:

def check_match(self, object):
    if isinstance(object, bool) or not isinstance(object, int):
      # We need to check for bool as a special case, since bool
      # is for historical reasons a subtype of int.
      raise exceptions.FormatError(
          'Got ' + repr(object) + ' instead of an integer.')

At the end of the day, this is what will we have:

ANY_INTEGER_SCHEMA = SCHEMA.AnyInteger()
ANY_FLOAT_SCHEMA = SCHEMA.AnyFloat()

[lukpueh]

obsolete via #776