New Serial Manager API:

SerialManager: provides access to serial ports
SerialPort: for reading and writing data to and from serial ports

IO with both array based and direct ByteBuffers is supported.

Accessing serial ports requires android.permission.SERIAL_PORT permission

Each platform must configure list of supported serial ports in the
config_serialPorts resource overlay
(this is needed to prevent apps from accidentally accessing the bluetooth
or other system UARTs).

In addition, the platform uevent.rc file must set the owner to the
/dev/tty* files to "system" so the framework can access the port.

Signed-off-by: Mike Lockwood <lockwood@android.com>