Changes

Makefile,contrib/jenkins: import from osmo-epdg

Add Makefile and contrib/jenkins.sh from osmo-epdg. Add "rebar3 asn
compile" to the "build" target, as mentioned in README.md.

Change-Id: Id8d6652c9007f4d565e2e0ca318e3a7b2113ea67
Tweaked-By: Vadim Yanitskiy <vyanitskiy@sysmocom.de>