Synchronizing sensord code with IIO driver support for accelerometer plugin

Synchronizing sensord code with IIO driver support for accelerometer plugin

The sensord code improvements are as follows:
  - sensor HAL plugin design has been changed to include common plugin code in sensor_hal parent
    class instead of individual sensor HAL plugins
  - the new plugin design allows easy modification for IIO or input based driver interface
  - sensor client library API has been changed
  - policy for loading plugins is based on configuration as well as the plugin directory path
  - code cleanup and bug fixes

Contributors:
Jae Hyun Jo <jaehyun7.jo@samsung.com>
Hyun-sung <hs81.go@samsung.com>
Kibak Yoon <kibak.yoon@samsung.com>
Amit Vithalrao Dharmapurikar <amit.vd@samsung.com>

Change-Id: I87776b07b6202af1c82ec4cdbff85df0553af8cb
Signed-off-by: Amit Dharmapurikar <amit.vd@samsung.com>