client_smpl.py: less aggressive bisect

At home I noticed that I download at 6.7 Mbit/s and the test
continues to request 7 Mbit/s of rate.

This is wrong, because instead the test should use 6 Mbit/s
as a rate when the speed is 6.7 Mbit/s.

This diff fixes the problem, by picking the element which is
at the left of the bisection point.

Tested from the Nexa Center with many close and far servers
to make sure the new code works both in normal conditions
and when we go past the boundaries of the vector.

While there tweak the code that prints the result of the
test to put the rate first, then the speed, because it
is simpler for a human (like me) to read the new output
(the rate is decided first, then comes the actual download
speed).
Use port 80 for the dash test

The new deployment of mlab allows us to bind() port 80, so use
port 80 for the dash test.
Makefile: adapt _install to also install modules
UNIX/etc/neubot: add the api and users configuration files
Makefile: make sure that we run install with umask 0022
Makefile: sort .PHONY targets
Makefile: better uninstall

Teach the uninstall target to attempt to remove all the directories
in which we install files.

We use `rmdir $DIR` to attempt to remove a directory, therefore,
if there are other files inside the directory, the directory is not
removed.

Tested by adding [ and ls inside $BINDIR and by checking that $BINDIR
is not removed by `make uninstall`.
Move bin/neubot to UNIX/bin/neubot

Now bin/neubot is the script to run neubot under UNIX, therefore
move it below the UNIX directory to avoid surprising people who
browses the tree.
UNIX/bin/neubot: adapt NEUBOT_HOME to new directory layout

With plugins we install $(DATADIR)/neubot/neubot (which contains
the core) and $(DATADIR)/neubot/mod_* (a directory for each plugin).

Therefore update NEUBOT_HOME to be $(DATADIR)/neubot.
Makefile: tweak the uninstall target

1. use `-mindepth 1` because there is no point in trying to
   delete the / directory;

2. we don't need to `rmdir {} \;`, therefore don't do it.
Merge branch 'feature_update_Makefile'
Makefile: change regress find(1) -perm to be more liberal

I typically use umask 077, therefore the -perm of find(1)
must be more liberal to catch executable files.
Repair regress/neubot/bittorrent/config.py
Repair the regress/neubot/http/rootdir.sh test
Preliminary step to repair regress/Makefile tests

I need to prefix neubot to all the files of the core of neubot, to ease
the comparison between the past and what we install now.
Repair the regress/Makefile tests
Merge branch 'repair_regress'
runner_policy: document the correct run-this-test probabilites
mod_dash/client_smpl.py: remember to include the system platform
mod_dash/client_negotiate.py: log when the test is done