add comments to elem_test "buttons", update db_dynamic_init.h

Signed-off-by: Yakov Goldberg <yakov.g@samsung.com>
add hash of op_prop by op_id

Signed-off-by: Yakov Goldberg <yakov.g@samsung.com>
add db init

Signed-off-by: Yakov Goldberg <yakov.g@samsung.com>
Merge branch 'develop': add test_button example