Feature/adr tutorial

This tutorial added in a basic introduction to using the ADRSolver and running an Advection-Diffusion problem. This is to setup in a new basics directory and contains some regression tests.

@ccantwel I do not seem to have permission to do the merge request in this sub repository so I guess you will have to do this one!

@ssherw Sorry, I have fixed the permissions, so you should be able to merge now.

mentioned in commit 0e6c1de2

Status changed to merged