add additional option set test
refine code
code refine
fix bug
1. add encoder-engine-decoder API UT for: IDR request, LTR request
2. add decoder api UT for EC: Disable/Enable EC
3. Fix a decoder bug when EC is disabled
   itoltalMbDec should be set to zero when encouter a new sequence/picture, even   when EC is disabled.
enlarge QP range when skipframeflag off on BitRate mode
Merge pull request #1351 from lyao2/bitrate_mode

enlarge QP range when skipframeflag off on BitRate mode
Merge pull request #1349 from dongzha/AddAPIUTEncoder_Decoder

add encoder/decoder api test for LTR and EC flag
Merge pull request #1350 from lyao2/ut_interface2

add encoder Interface additional option set test
Fix bug RC_QUALITY_MODE not works as expected
Fix bug RC_QUALITY_MODE not works as expected
Merge pull request #1354 from lyao2/fix_qualitymode_bug2

Fix bug RC_QUALITY_MODE not works as expected