Notifications enhancments


1. Introducing icons for popup notifications.
Unfortunately don't know how to make the paths to icons be created automatically based on blingbling location, so in udisks_glue.lua I had checked-in absolute paths as on my machine and also I had pushed the icons which I'm using to an icons directory.
2. Replaced abbreviation "Usb" with USB as a more readable one. 
3. Using filesystem for notifications as a useful data to know when device is mounte