Lightning Stream 0.2.2

The source of the two GNU LGPL libraries the Stream Gateway image (xbt-datum-gateway) links statically, exactly as its build used them: libmicrohttpd and argp-standalone, with SHA256SUMS-datum-gateway-lgpl. The rest of the source is this repository at this tag; scripts/datum_gateway_build.sh builds and links the gateway, so it can be rebuilt or relinked against modified versions of these libraries. The Linux package is the repository itself: see docs/LINUX.md.