Sidekiq jobs frequently spawn long-lived child processes to do work.
In some circumstances, these can be reparented to init when sidekiq is
terminated, leading to duplication of work and strange concurrency
problems.

This commit changes sidekiq so that, if run as a process group leader,
it will forward `INT` and `TERM` signals to the whole process group. If
the memory killer is active, it will also use the process group when
resorting to `kill -9` to shut down.

These changes mean that a naive `kill <pid-of-sidekiq>` will now do the
right thing, killing any child processes spawned by sidekiq, as long as
the process supervisor placed it in its own process group.

If sidekiq isn't a process group leader, this new code is skipped.

Markdown renderers find it easier to determine
where lists start and end when lists are surrounded
by new lines.

For consistency, also ensure entries in the list
are aligned when they span multipls lines.

For the sake of consistency, removes any extraneous
consecutive blank lines from the doc suite.