fix an errors that for single slice mode, the number of slices should be 1
Merge pull request #1262 from ruil2/fix_errors

fix an errors that for single slice mode, the number of slices should be 1
    use WelsEnc namespace instead of WelsSVCEnc
Merge pull request #1264 from ruil2/namespace_1

    use WelsEnc namespace instead of WelsSVCEnc
merge level table
Merge pull request #1265 from ruil2/namespace_2

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