Printable: initial requirements

[michaelwood]

Needed for printable pages:

• Printable: Bars in bar chart not showing #15
• Interface UI controls such as input boxes, non-selected filters, buttons, scroll bars etc shouldn't be visible on print
• Page breaks must not break in the middle of content such as graphs
• Minimise large blank spaces
• Report-like page

[mariongalley]

Not sure if this needs a separate issue, but can we add a button that advertises this feature more obviously? I think we could do with a big "Download report" call to action so that users know it's available even if they aren't trying to print the page (lots of people don't know you can turn a web page into a PDF using the print function, or if they're like me, don't trust the print version to look good)