start_qemu.sh: also allow graphics emulation

[jurobystricky]

Currently the script explicitly disables support for graphics, via:

...
    -vga none -nographic \
...

However, there does not seem to be any particularly good reason not to allow graphics via something like

    -vga std \

The user/developer should be able to chose the type of emulation via a command line option (something like --enable-graphics). Or there could be two different scripts.

I tested this with an image I mixed:

 "Bundles": [
  "os-core",
  "os-core-update",
  "desktop-autostart",
  "kernel-kvm",
  "sysadmin-basic"
 ],
...

and manged to boot the resulted image (with the modified script) into a desktop environment.

[phmccarty]

@jurobystricky I would prefer keeping the single script and adding the ability to choose whether to boot the VM with graphics or not.

The script doesn't have command line options at the moment; it just has the one positional argument, and will read VMN from the environment. IIRC, that acronym stands for "virtual machine number". I am open to adding command line options, but of course, it would be nice to preserve backwards compatibility for current users. Given that the script is pretty basic at the moment, backwards compatibility would be straightforward to support.