sensord: ipc: add channel class

sensord: ipc: add channel class

- channel class is a nexus to a socket which is capable of I/O operations,
  such as read, write, connect, and bind.
- channel class provides:
  - the current state of the channel.
  - the configuration parameters of the channel.
  - the I/O operations that the channel supports.
- channel class can support synchronous/asynchronous send/read call.
- channel_handler:
  - is called by all I/O events(connect/disconnect/read and error)

Change-Id: I85365e7cb443e969653353a83f8110ab690c4303
Signed-off-by: kibak.yoon <kibak.yoon@samsung.com>