Mv level work1

I took a series of constants and put them into a static structure such that I can vary the constants by level (instead of one set of constants for all levels).  Then I found all places in this file that had special "if (level==0)" code and changed it to "if (m_LevelTraits[level].m_OverlappedFiles==true)".  Finally, some code relating to the m_MaxGrandParentOverlapBytes constant was disabled.

Testing shows a 48% increase in write throughput.  Slight increases in read and iterate throughput, but not worth mentioning.