Use the param "appName" to set the title of the document

[glughi]

What this PR does

Fixes TerriaJS/TerriaMap#690

Use appName from config.json to set the title of the web page.

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]

Hi @glughi,

Thanks for your PR.
For various reasons, it is best to set the application title from terriamap instead of from the Terria instance (for eg, Terria could be instantiated from a non-browser context like nodejs. We also don't assume a page to have just a single instance of Terria).

I have created a PR in terriamap to do this. Let me know if it'll work for you - TerriaJS/TerriaMap#700
Thanks.

[glughi]

Yes, it works!