`gpkg_create_dummy_features()` upgrades and deprecation

[brownag]

• [x] Use new gpkg_create_spatial_ref_sys() function internally
• [x] Abstract out gpkg_geometry_columns table create/insert code as new functions
• [x] Deprecate gpkg_create_dummy_features() function name and replace with e.g. gpkg_create_empty_features()
• [x] Deprecate gpkg_contents(template=) argument, provide documented arguments for each data element (srs_id, bounding box)
• [ ] Add a gridded analog e.g. gpkg_create_empty_grid()
• [x] Add an option to add empty tables to gpkg_contents (default to TRUE, changing existing behavior)