overhaul README

remove some incorrect/obsolete notes + the section about the
half-baked "sabotage-in-userspace" mode, and mention recent
improvements.
README: more fixes
README: add bitcoin donation address.
add python-websocket
add python-simplejson
enter-chroot: allow config file to be set via env

that way one can make shell scripts to easily chroot into different
rootfs.
man: update to latest
busybox: better patch for tar xz support
musl: bump to 0.9.14
python: debloat
perl: debloat

the perl manpages are roughly 20MB.
usually the approach taken by sabotage is to install manpages,
however in this case it takes ca 30% of the entire install size.
additionally, the generated manpages use nasty syntax the manpager
can't deal very well with anyway.
and there's still perldoc, so only the documentation for built-in
modules is missing.
an interested perl developer using sabotage can still read them online,
or he can just edit the package file and undo the removal.
openssl: fix install path for manpages
openssl: debloat
screen: put sockets into $HOME instead of /tmp

on suse, the socket is put into /var/run, which makes more sense
than /tmp.
imo it's even better to put them into home, so other users can not
even see other users sockets.
the only drawback of that is that screen will not work on a read-only
fs (where /var and /tmp are typically on tmpfs and thus writable).
screen: fix breakage when used with run-emulator.sh

when the sabotage rootfs is used in qemu with virtio mount,
new files created get the uid of the qemu user, not the uid of the
user inside qemu. this is usually no problem since you have full
access permissions to everything - however, screen did some uid
comparison checks, which only make sense when the screen sockets
are stored in a public place such as /var/run or /tmp.
in our case, they are stored in $HOME, so any screen there belongs
to us and we do not need to compare uids.
add eudev

to address one of the issues raised in #125.