MB-9477: generalized parse_validate_number/3 for floats

Change-Id: I2fe16f8699d44bf4c25860fb3fa4fde3336dca05
Reviewed-on: http://review.couchbase.org/30107
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>