Replaced bat.png and bat_icon.png with Bareos Logo and added bat.svg

The Bat Icon was a brain before, now it is the Bareos Logo.
Also added bat.svg from which the .png files were exported.

Fixes #84: Bat Icon is a brain, we should change to the Bareos Icon

Signed-off-by: Marco van Wieringen <marco.van.wieringen@bareos.com>