Feature/andrembcosta/pressurized phase field

[andrembcosta]

Adding new kernels for phase-field fracture model in a pressurized environment. This is similar to Frank's work, but the pressure field are assumed to be constant (they will be solved for using EFEM/EDFM in a global domain and this model will only be applied in the vicinity of crack tips).

This PR add kernels for the terms in red (green terms are the standard phase-field equations). Terms in the first equation are in SolidMechanicsSmallStrainQuasiStaticPressureKernel.hpp, whereas the terms in the second equation are in PhaseFieldDamagePressureFEMKernels.hpp.

The kernels are written using the PDEUtilities functions from https://github.com/GEOSX/GEOSX/pull/1600. New Linear and BilinearFormUtilities were added for H1 spaces.