UMS [3/6]: Add UsbDebuggingManager and UsbDebuggingActivity to LegacyUsbManager

The UsbDebuggingManager listens to adbd requests and displays a dialog
when the public key authentification fails, for the user to confirm if it
wants to allow USB debugging from the attached host. If the user chooses
to always allow USB debugging, the UsbDebuggingManager writes the public
key to adbd's config file so that the public key authenfication succeeds
next time.

1: https://gerrit.omnirom.org/#/c/5041/
2: https://gerrit.omnirom.org/#/c/5042/
4: https://gerrit.omnirom.org/#/c/5044/
5: https://gerrit.omnirom.org/#/c/5045/
6: https://gerrit.omnirom.org/#/c/5046/

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: I819b8a0428ba34b68dadeb9fa67c53abb9a85fbc
Merge "UMS [3/6]: Add UsbDebuggingManager and UsbDebuggingActivity to LegacyUsbManager" into kitkat