This patch adds detailed documentation for HFSC scheduler. It roughly
follows HFSC paper, but tries to not rely too much on math side of things.
Post-paper/Linux specific subjects (timer resolution, ul service curve, etc.)
are also discussed.

I've read it many times over, but it's a lengthy chunk of text - so try
to be understanding in case I made some mistakes.

tc-hfsc(7): explains algorithm in detail (very long)
tc-hfsc(8): explains command line options briefly
tc(8): adds references to new man pages
Makefile: adds man7 directory to install target
q_hfsc.c: minimal help text changes, consistency with tc-hfsc(8)
Signed-off-by: Mike Frysinger <vapier@gentoo.org>