Refactor foreground and background styling

[Luke Matthew Sutton]

Currently every view needs to implement these themselves, but often they could just use some generic styling. There are some exceptions — such as views which consist of multiple components — in which case these could implement their own styling in addition.

• Background colour
• Background pattern; this is actually setting a character to a cell + foreground styling
• Foreground colour
• Borders; a generic container which just draws a border around its contents