Early gzip compression work

CHANGELOG.md

api/r0/download.go

api/r0/thumbnail.go

api/webserver/route_handler.go

common/config/conf_min_shared.go

common/config/models_domain.go

config.sample.yaml

...ollers/thumbnail_controller/thumbnail_resource_handler.go

controllers/upload_controller/upload_controller.go

migrations/19_add_compressed_flag_down.sql

migrations/19_add_compressed_flag_up.sql

storage/datastore/datastore_ref.go

storage/datastore/ds_file/file_store.go

storage/datastore/ds_ipfs/ipfs_store.go

storage/datastore/ds_s3/s3_store.go

storage/stores/media_store.go

storage/stores/thumbnail_store.go

types/media.go

types/object_info.go

types/thumbnail.go