- Add usual CSS tricks to expert.css
- Don't display steps and states for expert.
  This make the layout of command line instructions much easier, and
  experts don't need them anyway :)
- Prepare the work for the Debian scenario.

The additional complexity is needed to allow at the same time:

  - Elements that are either in 'usb' or clone 'scenario'.
  - Elements that are specific to an OS.
  - QR codes and URLs that are specific to a single scenario.
  - Bits that are common to several OS but not all.

We also have to distinguish between <span> and <a> which are "inline"
and <div>, <img>, and <p> which are "block" because the "initial" value
of the "display" property is not available on IE.

See http://www.w3schools.com/cssref/css_initial.asp

Conflicts:
	wiki/src/install/debian/clone.mdwn
	wiki/src/install/inc/steps/switch.inline.mdwn
	wiki/src/install/inc/stylesheets/usb.css
	wiki/src/install/linux/clone.mdwn
	wiki/src/install/linux/usb.mdwn
	wiki/src/install/mac/usb.mdwn
	wiki/src/install/win/clone.mdwn
	wiki/src/install/win/usb.mdwn

Restarting this second time might be problematic as well, and
differently than the previous one (see 9bcda2d5). So we can't take for
granted that the final Tails will work before we restarted on it.

The additional complexity is needed to allow at the same time:

  - Elements that are either in 'usb' or clone 'scenario'.
  - Elements that are specific to an OS.
  - QR codes and URLs that are specific to a single scenario.
  - Bits that are common to several OS but not all.

We also have to distinguish between <span> and <a> which are "inline"
and <div>, <img>, and <p> which are "block" because the "initial" value
of the "display" property is not available on IE.

See http://www.w3schools.com/cssref/css_initial.asp

  - Say "new" instead of "second"
  - Say "other" instead of "temporary"
  - Don't say "final"