Use socket for IPC of focus APIs instead of the DBus

Use socket for IPC of focus APIs instead of the DBus

The benefits of this change are here.
 - Connection is established when registering a focus node. This leads to
   remove the previous signal handler for cleaning focus resources.
 - Response time is enhanced as per the change of IPC.(DBus to socket)

[Version] 0.12.20
[Issue Type] Enhancement

Change-Id: Ifbc3ecde29985e9150ed7429b8616ef6cbe99d92
Signed-off-by: Sangchul Lee <sc11.lee@samsung.com>