api: add -m/--subme to adjust level of subpel refine

This is very similar to x264, but ours has no effect on RD analysis, it only
affects the amount of HPEL and QPEL refinement for motion estimation.

--HG--
extra : amend_source : 191f7e10286e09fa12a8e8309ebfc469fa490efe
TEncSearch: remove unused m_searchMethod
TEncSearch: remove unused m_searchRange
motion: subpel offsets table needs a 'no-motion' entry