Support new extra preview mode

Support new extra preview mode

- The defined extra preview mode
 : MM_CAMCORDER_EXTRA_PREVIEW_MODE_CAMERA_CONTROL
 : MM_CAMCORDER_EXTRA_PREVIEW_MODE_PIPELINE_SRCPAD -> Changed from MM_CAMCORDER_EXTRA_PREVIEW_MODE_VIDEO_PAD
 : MM_CAMCORDER_EXTRA_PREVIEW_MODE_PIPELINE_ELEMENT -> New
- Minor change
 : Add sub function to get element and element name.
 : Make some functions as static.

[Version] 0.10.270
[Issue Type] New feature

Change-Id: If1d2188aae227ee32437cd2409c2ee2226143dec
Signed-off-by: Jeongmo Yang <jm80.yang@samsung.com>