create a release workflow

[x1ddos]

sysupdates, however dumb the current version is, is up and serving.

so, should start publishing releases and push them through the sysupdates:

one-off tasks:

• nd and ngui should have a -version flag
• make a sig keypair
• write a "making a release" doc

every release:

• tag a commit with a "release candidate"
• produce nd and ngui binaries at the tag
• sign and publish tar.gz'ed binaries
• add the release to a dev channel of sysupdates
• if all goes well, tag with a release and repeat the above

i may have forgotten something