border-screen: Optional border around screen (#63)
Add option to specify border for screen / window in configuration file.
Can be useful when user turn off window decorations and need a subtle hint or want strong window borders.
This MR simply draws to the surface right before it is deployed. Border
is only drawn if setting is set in
terminalrc. It draws over existing
surface - hence any text etc. - but only 1px? wide + uses
which accumulates layers.
Ref issue #63