Enhance ability to support legacy datum transformation definitions

[Norm Olsen]

The RFC 2 implementation included the conversion of all datum transformation definitions (previously maintained in the Datum Dictionary) to the new form of datum transformations as defined by a record in the Geodetic Transformation Dictionary. This appears to work fine for geodetic transformation definitions included in the standard CsMap distribution.

However, it is often the case where end users of applications using the CsMap library have created custom datum definitions (implying a custom geodetic transformation). It would be nice if the CsMap distribution included a/some feature(s) which would support the automatic conversion of such datum definitions to the Geodetic Transformation dictionary format.