monitor: Add request-server and request-handler-thread

monitor: Add request-server and request-handler-thread

To provide libpass API via socket, a manager is required to
manage network connections and requests from clients.

Request-server is a manager to manage network connections.
It accepts and establishes a socket connection from each
client, then spawns a per-client request-handler-thread to
deal with incoming requests from the client if required.

Change-Id: I17cdf1fde69022663c2369b55982ac43e5b5c688
Signed-off-by: Sung-hun Kim <sfoon.kim@samsung.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Dongwoo Lee <dwoo08.lee@samsung.com>