Add video meta for video encoder

Add video meta for video encoder

Some encoder plugin needs video meta from GST buffer,
but GST buffer from media codec did not provide video meta.
This patch sets video meta to GST buffer.

- Changes
 : Change return type for mc_caps_new()(GstCaps* to gboolean).
 : Add new functions for video info and meta.
 : Remove gst_caps_unref() in mc_gst_prepare().
   gst_caps_unref() can be called although it's freed after pipeline is released all.

[Version] 0.6.32
[Issue Type] Improvement

Change-Id: Iefb2e17bee72a3e7a72bdf952f8c0fa2e2f98dd4
Signed-off-by: Jeongmo Yang <jm80.yang@samsung.com>