turn QuadraturePoint.weight and QuadraturePoint.coord public
Add Model2D operations for influcence radius and improve operations for search

  - add a boolean parameter in search() to switch whether filet nodes by influence radius
  - add searchNodesSegments()
  - add influcenceRad support
    + filetNodesByInfluenceRad()
    + getInfluenceRad()
    + setInfluenceRad()
    + setInfluenceRadForAll()
Extract interface ModelSearcher from Model2D

  - also rename Model2D.search() to Model2D.searchModel()
Add some getter function to Model2D

  - maxInfluenceRad(), getPolyton(), getSpaceNodes(), getAllNodes()
Rename package tsmf.weakform to tsmf.assemblier
build interface ConstitutiveLaw and implement it as IsoElastic2D

  - create package tsmf.cons_law
  - also add planeStress() factory in IsoElastic2D
Implement TimoshenkoAnalyticalBeam2D as a calculator of the famouse cantilever