Wifi notifications: notify when wifi connects [2/2]

Options:
  off (default)
  a dry white toast
  a notification
  a notification with a sound
For those of us that survive on wifi islands in small college towns this is
pretty nice to have
Any notification within 30 seconds of broadcast intent ACTION_BOOT_COMPLETED
will be canceled to prevent startup notification spamming. 8 (default) of the
previous connections are remembered and it will update the notification's content
accordingly if you've restored a connection.
PS2: clean up strings
PS3: fix build & fix list preference not being updated
Change-Id: I18448773c64a6a0d65e7c39d008de2b371f4d556