Change ScoreInfo's score_type in outputmetadata to string

Change ScoreInfo's score_type in outputmetadata to string

score_type in ScoreInfo outputmetadata was integer value which an user doesn't understand
even though it was provided for the user convenience.
So they are changed to string and user can understand what they mean.
The string values are parsed and converted to proper enumerations.

Change-Id: I9f09bb6f2c534ff5a8f5084a3e2413514b075f5d
Signed-off-by: Tae-Young Chung <ty83.chung@samsung.com>