Use of MIRCO in a single-scale setting

[jacopenji]

When MIRCO is used to solve a single-scale rough contact problem, no iterative correction step is necessary. This can be easily achieved by setting the related maximum iterations number to 1 in the input file. Though, in this case an error message is thrown.

A simple warning message would guarantee that the user knows what is going on without interrupting the calculation and without the need of additional modifications.

[mayrmt]

I'd prefer to make this more explicit for the user: if I want to run MIRCO in "single-scale mode", then I should indicate this somewhere in the input and then everything else should happen by itself. As a user, I do not want to know about the internals of the implementation and how I need to limit certain iterations to achieve a single-scale simulation. Similarly, if I want to run in "multi-scale mode", this should be passed to MIRCO on input.