Managing active/inactive elements and nodes

Add surface node search

add getGeoType() to GeoObject class and its child classes

Petsc vector

PETSc related cmake changes. MacOS.

Change include syntax for lis.h and petscksp.h. Documentation. Formatting.

MeshAnalysisDialog update

Try to fix Vector3 default constructor tests on travis

Try to fix some failing tests on travis CI for Vector3 associated to default constructor of Vecor3.

Cleanup in MeshLib: Removed reviseElement() methods.