Test AdaptiveCellEdge and build QuadrangleAdaptiveCellFactory

  - QuadrangleAdaptiveCell haven't been tested.
Trivally loosen the err limit of SymTriangleQuadratureTest.java
Move inner class Mixer and PostProcessor out of WeakformProcessor2D
Make Mixer and PostProcessor independent to WeakformProcessor2D

  - also remove redundent lagDiri field of WeakformProcessor2D
Build interface SynchronizedClonable and package util.synchron

  - also make MLS, LagrangeWFAssemblier, PenaltyWFAssemblier implement it
extract processing codes to WeakformProcessRunnable

  - also make SynchronizedItratorWrapper for extracting
Remove unnecessary maxInfluenceRad as field of WeakformProcessor

  - also remove redundent maxInfluenceRad argument of Mixer and PostProcessor constructors
Make RadialFunctionCore a specific interface

  - an interface extends UnivarArrayFunction and SynchronizedClonable
  - upgrade TripleSpline and Wendland accordingly
Add SynchronizedClonable and addToMainMatrix() method in WFAssemblier

  - also update LagrangeWFAssemblier and PenaltyWFAssemblier
  - LagrangeWFAssemblier decorates PenaltyWFAssemblier (not inherents)
  - make a safe copy of ConstitutiveLaw's matrix in PenaltyWFAssemblier
Make BasisFunction extends SynchronizedClonable

  - also update MonomailBasis2D
make ShapeFunction implements SynchronizedClonable

  - update MLS and Linear2D accordingly
put away constants in WeakformProcessor2D, move DEFAULT_CAPACITY to Mixer
Roughly implement multi-thread WeakformProcessor2D

  - Timoshenko cantilever beams tests seams good
  - WeakformProcessRunnable add observerable feature
  - add WeakformProcessorRunnerObserver interface