Clean up the last remnants of CUSTOMURL support that was silently
removed by commit ce2138c72bab5867c172ee2776d1e27dc34c01d1.
Remove SUBARCH option that was introduced in
ab66b6ff8608203999a41f47283ea1e9304bb868 but never implemented.
refactor how lxc.arch settings are figured out
Rip out $SUBARCH and merge its functionality into $ARCHVARIANT
Add a nice selection menu for ARCH and ARCHVARIANT and update docs
Add manual Qemu setup instructions
I think this is redundant as LXC will assume native arch.

furthermore, ARCH is set to an appropriate value during configure().
While those using custom tarballs should specify it by themselves
(I mean, we could parse it out of the tarball filename *assuming*
the tarball contains one of the values of the arches array and even
then the only valid ones would be amd64 and x86 due to LXC not
giving a fuck about others).
I guess the final answer will be given when direct Qemu emulation
support is added.
Hmmm... why are we giving paths inside the container using absolute
paths on the host?
fix proc security ... almost

Mounting proc ro prevents security vulnerabilities such as changing the
default handler for loading modules (this one is really ancient...):

after mounting it ro:
vm proc # echo "/sbin/modprobe" > sys/kernel/modprobe
-bash: sys/kernel/modprobe: Read-only file system

and with sys_admin capability dropped:
vm proc # mount -o remount,rw /proc
mount: permission denied

Note that I managed to totaly freeze my host system by doing
grep -r lxc /proc
inside the container. Unfortunately I don't know how to fix this one.
And I don't know whether this is a problem of Linux itself or it
happened because I'm not on vanilla Linux.
Update documentation to match code
Base $CONFFILE on $NAME rather than $UTSNAME and beef it up.

I always thought $UTSNAME and $NAME were "seperate" and that this
functionality was there to handle corner cases such as having multiple
virtual machines with the same hostname (perhaps a production and a
staging one? or maybe to seperate it based on the network it was in?).
Quoting fix Mk. 1

I tried to create a container with whitespace in its name ...
my root filesystem didn't like it.

broken into two commits to easily see the changes, should anyone ever
have the need to do so in the future.
Quoting fix Mk. 2

Actually, passing whitespace for container name doesen't work smoothly
yet, since the veth (host part) interface doesen't accept whitespace.

But the script does create the rootfs and config file without
changing/adding "random" files all over host's filesystem.
Merge pull request #62 from specing/fetch_fixes

Loads of fixes and updates from specing.