Make PenaltyWFAssemblier adapt for null volumn force values
fig a bug of Model2D.initOutput

  - the bug mistakenly let null "segs" be legal
fig same bugs in WFProcessor functions

  - the bugs are that inner variable segs doesn't initiate properly
    + processBalance()
    + processNeumann()
    + processDirichlet()
implement NeedPreparation in WFProcessor2D
Add TimoshenkoProjectProcess() and main() in WFProcessor2D

  - just can run without Exceptions, need further tests