Content mostly unchanged since v9.9

This update is "minimal" in that it mostly reflects the removal of the 'area'
table, replaced now by 'extent', 'scope' and 'usage'

Other new aspects of EPSG v10 are left aside.

Minor update w.r.t 9.5.5 that adds a few new coordinate operations.

This work mostly consists of:
- a C++ implementation of the ISO-19111:2018 / OGC Topic 2
  "Referencing by coordinates" classes to represent Datums,
  Coordinate systems, CRSs (Coordinate Reference Systems) and
  Coordinate Operations.
- methods to convert between this C++ modeling and WKT1, WKT2
  and PROJ string representations of those objects
- management and query of a SQLite3 database of CRS and Coordinate Operation definition
- a C API binding part of those capabilities

This is all-in-one squashed commit of the work of
https://github.com/OSGeo/proj.4/pull/1040