Tied contact isn't really a contact model, it is a specific 'case' in which contact enforcement is used. The contact model is meant to handle constitutive type models/response. Here we move TIED to the contact case, and delineate tied in the normal direction from tied 'full', which includes normal and tangential (there is no foreseeable use case for tied only in the tangential direction).
Move TIED to be a contact case
Include TIED_NORMAL (implemented) and TIED_FULL (tangential component not yet implemented).
Pushed these changes down to the physics.
Light refactor of the switch statements used to call the common-plane routines (more invasive design refactor beyond the scope of this PR)
Added plumbing for adhesion based separation law in contact model, though not yet implemented.
Updated all coupling scheme checks accordingly (I think :) )
Tied contact isn't really a contact model, it is a specific 'case' in which contact enforcement is used. The contact model is meant to handle constitutive type models/response. Here we move TIED to the contact case, and delineate tied in the normal direction from tied 'full', which includes normal and tangential (there is no foreseeable use case for tied only in the tangential direction).