Include comparison yaml files in default configuration

[chrispcampbell]

When I added support for defining comparisons in yaml format in #315 (like we already had for checks), I stopped short of making changes in plugin-check so that comparison files are detected automatically.

I will change plugin-check (the template-tests code specifically) so that it picks up comparison yaml files with the following glob pattern:

{projDir}/**/comparisons/*.yaml

The current default glob pattern for check tests is:

{projDir}/**/*.check.yaml

We can continue to accept that one (for backward compatibility, since the create package was using that format until now), but will amend it to also include files under a checks directory:

{projDir}/**/*.check.yaml
{projDir}/**/checks/*.yaml

I will update the create package to generate files in the new recommended layout (this is what we have used for En-ROADS and C-ROADS):

model/
  {model}.mdl
  checks/
    checks.yaml
  comparisons/
    comparisons.yaml

The reason for the extra level of directories is that most projects will eventually have more than one yaml file of each variety, so this is more future-proof.

I will also update the existing sir and hello-world examples to use this recommended file naming and layout.