Epoch limitation in GeoPackage WKT Extension

[jamesresslernga]

Supporting the use of Epoch in GeoPackages for the DGIWG GeoPackage profile (to be edition 1.1), related to issue #675, found a limitation that could be addressed by the SWG.

Because the gpkg_spatial_ref_sys has a single row for each srs_id (primary key) in a GeoPackage, the definition of Epoch for a GeoPackage is limited to one Epoch date per CRS. Without using multiple srs_id values, multiple epoch dates for gridded data with the same srs_id must be stored in distinct GeoPackage files.

How would uses embed 2 different elevation tile matrix sets with the same CRS that were collected at two different time? Could be necessary it the difference is significant number of years.

[rouault]

Because the gpkg_spatial_ref_sys has a single row for each srs_id (primary key) in a GeoPackage, the definition of Epoch for a GeoPackage is limited to one Epoch date per CRS

Just create one entry per (CRS, epoch) tuple that will have its own srs_id. Similarly to what was discussed in #676 (comment) and #676 (comment)