add function pointer
Merge pull request #591 from sijchen/me_merge91

[Encoder ME] add function pointer initialization
    add preprocessing parameter for screen content
Merge pull request #592 from ruil2/enc_processing

    add preprocessing parameter for screen content
add ExpandPic encoder unit test
Merge pull request #593 from ganyangbbl/encUT_ExpandPic3

add ExpandPic encoder unit test file
    add scene change detection in workflow for screen content
Merge pull request #596 from ruil2/enc_processing

    add scene change detection in workflow for screen content