scan-registers: determine available notifications

00 is documented in HID++ 1.0 specification, it should be safe to set the 00
register. As another program may have written the notifications register
already and since enabling notifications has side-effects such as "disabling"
certaing functions, restore the flags after reading out available notifs.
get rid of bad map() calls
window popup fix for kwin

also, only try to position the window next to the status icon if it has never
been shown before
minor tweaks
re-work the status icon updating
version and url fixes
status icon menu items open the right device window
debian version update
Merge pull request #41 from Lekensteyn/tool-updates

scan-registers: determine available notifications
enable notifications for peripherals; fixes #27
only enable certain notification flags on devices

Also added some documentation to the notification flags, where possible.
minor readme update
only notify on connected devices at start-up