This is more in line with the other document names.

Also, change the title to simply "Ganeti installation tutorial".

Reviewed-by: ultrotter

In case one installs from source, make, tar and gzip are also needed. tar and
gzip are almost always installed, but make not, so let's add a note about that.

Also remove a '>' in the apt-get install example so copy-paste works.

Reviewed-by: imsnah

This removes the section on packages from installing.sgml (until we have
packages) and adds/corrects informations about using the startup script.

It also adds notes about the ``--master-netdev`` option, which one needs
to use if the node doesn't have an interface named xen-br0 (or if it's
not the interface wanted for external access).

This changes installing.sgml, adding details about required software and
OS instances. It also updates INSTALL and README to correspond with the
sgml manual.

Reviewed-by: ultrotter

Reviewed-by: iustinp

Reviewed-by: iustinp