Revisit numerical types in metadata

[desruisseaux]

Interfaces in org.opengis.metadata packages use very specific types for numerical values, for example java.lang.Integer (fixed to 32 bits) or java.lang.Double (fixed to 64 bits). Those types are not always appropriate; an implementation may need to use a Long or even a BigInteger instead than 32 bits integers, or a BigDecimal instead than IEEE 754 floating point. We should leave that flexibility by using the more general Number type instead than a specific subtypes. In particular for the following properties:

• MD_FeatureTypeInfo.featureInstanceCount: 32-bits integer type is insufficient.

For floating point values, many of them are actually measurements. For those ones, we should consider javax.measurement.Quantity.

Historical note: the decision to use specific subtypes was done in the GeoAPI 2 days for compatibility with technologies like JAXB or Hibernate. But even with this goal in mind, abstract types could have been used with the help of adapters.