Introducing thickness and trenching in Palace

Idea is to have a full 3D simulation that physically simulates the finite thickness of the deposited metal and trenching in the dielectric (e.g. due to etching of the exposed dielectric regions):

• Eigenmode simulation of side-coupled resonator **(trenching only)**
• Eigenmode simulation of side-coupled resonator **(metal thickness only)**
• Eigenmode simulation of side-coupled resonator **(metal thickness and trenching)**