gpkg 0.0.12

Major cleanup and more consistent use of internal SQLiteConnection usage to ensure open connections don't get garbage collected
Added gpkg_disconnect() convenience methods for tbl_SQLiteConnection and src_SQLiteConnection
Added gpkg_connection() a user-level function for accessing or creating SQLiteConnections given a geopackage object or a path to GeoPackage file

gpkg 0.0.11

Added [ and [[ methods for accessing/replacing tables in a geopackage object
Replaced vapour functionality for driver detection with gdalraster equivalents

Added gpkg() alias for geopackage()
Added gpkg_create_geometry_columns(), gpkg_geometry_columns() and gpkg_add_geometry_columns()
Added gpkg_sf() convenience method for creating an sf object from tables. Defaults to a sf tbl_df, use as_tibble=FALSE for data.frame.
Now using new gpkg_create_spatial_ref_sys() function internally to ensure GeoPackages have the minimum required tables
gpkg_collect() and gpkg_table(collect=TRUE) gain support for selecting a subset of columns of interest
Deprecate gpkg_create_dummy_features() function name and replace with gpkg_create_empty_features()
Deprecate gpkg_contents(template=) argument, provide new arguments for each data element (SRS ID and bounding box)

Implemented GDAL driver detection for file paths via {vapour} for #15
Implemented functions for creating gpkg_spatial_ref_sys table and adding or removing spatial reference system records:
- gpkg_create_spatial_ref_sys(), gpkg_add_spatial_ref_sys() gpkg_delete_spatial_ref_sys(), gpkg_list_srs()
Implemented basic gpkg_validate() routine (will be expanded)
- Checks that gpkg_contents and gpkg_spatial_ref_sys exist
- Checks that at least one tile or vector dataset (with at least 0 rows) is in the database and gpkg_contents

Full Changelog: 0.0.8...0.0.12