Client bugfixes

Support for yggdrasil 0.4.5+

Merge pull request #21 from MassMesh/add-goreleaser-fix-1

Disable the binary count check in the goreleaser archive step.

Switch to GRE tunnels. From this version, autoygg is only compatible

with Yggdrasil 0.4.0 and newer.

Bugfixes. Add tests. Add packaging for Arch. Add Prometheus metric fo…

…r number of valid leases.

Add support for all four operating modes, and clarify specification

document accordingly. Add tests for all four operating modes.

autoygg-client: bugfixes: config peer detection on non-openwrt platforms

now works. change: blackhole routes are now no longer added.

autoygg-server: bugfix: on shutdown, make sure to tear down the default
route in the mesh routing table if one was added on startup. refactor:
make the config names of the firewall commands consistent with all other
configurable commands. feature: add lease expiration.

autoygg-server: add vpn support, add documentation, reconfigure Yggdr…

…asil for active leases after Yggdrasil and autoygg-server are restarted (e.g. after reboot)

autoygg-client: various bugfixes and more tests

client and server: version numbering improvements; add systemd unit f…

…iles; various bugfixes