Change displacement parameters in contact to read in a displacements vector

[tonkmr]

Description of the enhancement or error report

Tensor mechanics has switched so that the displacements are passed in as a vector:

displacements = 'disp_x disp_y disp_z'

It would be nice if the contact block changed to follow a similar syntax

Rationale for the enhancement or information for reproducing the error

It simplifies things for users if the tensor_mechanics and contact modules use similar syntax. It would also make things clearer for 2D axisymmetric simulations

Identified impact

The contact action will need to change. There may be other required changes as well.

[tonkmr]

@bwspenc and @jasondhales this is really just a suggestion, but I think it would make things a lot cleaner and clearer.

[bwspenc]

@tonkmr I think this is a great idea. I'd like to switch everything that needs displacements over to this syntax.