Remove a lot of boilerplate by using the errgroup package instead of
our own custom cumbersome solutions. Control server lifetime with an
outer Context.

Causes a slight reduction in boilerplate, and gets rid of a bunch of
custom logic for command-line parsing that is no longer needed.

Fix also some errors in the status template, and update to Bootstrap
4.3.1 and JQuery 3.4.0.

Also add instrumentation for the load balancer module.

Includes a merge of radiod and redirectord, updates to more modern Go
idioms, adoption of the higher level etcd concurrency primitives, and
a lot of other minor implementation changes.

The refactor is still incomplete: the daemons won't compile and the
code to start the RPC servers is missing.