Add printable stylesheet

[gregmac]

Would be nice to have a stylesheet that enables nice printing of the UI.

This should have:

• all UI controls (buttons, inputs) and "try it out" functionality hidden
• all items expanded
• header removed
• page width constraints removed (fluid layout)

Looks like the existing stylesheet should be split out (since it's only for "screen" now) so relevant sections can be re-used for the printable version.

[mjhaller]

+1

[stanleysantos]

+1

[fehguy]

see #460. Not every request in here is covered but basic functionality is there.