Add mesh block au region mapping

[micholm]

add region mapping for mesh blocks

What this PR does

Fixes #

This is a description of what I've done in this PR, especially explaining choices made to make the reviewer's job easier. If I don't replace this paragraph with an actual description, my PR will probably be ignored.

Test me

How should reviewers test this? (Hint: If you want to provide a test catalog item, create a Gist of its catalog JSON, add its url and your branch name to this url: http://ci.terria.io/<branch name>/#clean&<raw url of your gist> , and then paste that in the body of this PR)

Checklist

• There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
• I've updated relevant documentation in doc/.
• I've updated CHANGES.md with what I changed.
• I've provided instructions in the PR description on how to test this PR.

[na9da]

LGTM.

Tests failing, maybe we need to increment this constant to 155?

Might be good to add a line to CHANGES.md.

[micholm]

LGTM.

Tests failing, maybe we need to increment this constant to 155?

Might be good to add a line to CHANGES.md.

Ohh totally forgot about this const. Thanks :)