Start using boundary condition factory in apps

...luteGravityCurrents_Case1/DiluteGravityCurrents_Case1.cpp

...luteGravityCurrents_Case2/DiluteGravityCurrents_Case2.cpp

...luteGravityCurrents_Case3/DiluteGravityCurrents_Case3.cpp

...luteGravityCurrents_Case4/DiluteGravityCurrents_Case4.cpp

...luteGravityCurrents_Case5/DiluteGravityCurrents_Case5.cpp

...luteGravityCurrents_Case6/DiluteGravityCurrents_Case6.cpp

...luteGravityCurrents_Case7/DiluteGravityCurrents_Case7.cpp

...luteGravityCurrents_Case8/DiluteGravityCurrents_Case8.cpp

apps/gpu/FlowAroundSphere/FlowAroundSphere.cpp

apps/gpu/LidDrivenCavityGPU/LidDrivenCavity.cpp