added a minimum layer thickness parameter to the layer mesh generation process
adjusted the dialogue to ask for the new param
[ML] Const correction, variable locality.
[ML] Replace throw with assert in DenseMatrix::op().
Merge pull request #548 from endJunction/DenseMatrixOptimizations

Dense matrix optimizations
clarified comment
applid validator for minimum-thickness widget
Merge pull request #547 from rinkk/MinThicknessLayers

Layered meshes with minimum thickness layers