Allow bundling all available DB adapters in tinode binaries.

In addition to specifying the DB adapter explicitly via build tags,
allow bundling all available DB adapters to the binary (enabled via "all" tag).
The adapter may be chosen by setting `store_config.adapter_name` field in `tinode.conf`.

Modify build scripts and docker configs to support this.
Docker tinode-all image includes the bundled binaries, the adapter may be
chosen by providing ADAPTER_NAME env var.