1757 tm new routing

[soyarsauce]

See: TerriaJS/terriajs#3494

Still to do

• Create an "app-loaded event" to listen for when generating the html instead of a fixed timeout
• Generate sitemap.xml with routes generated from generate-init-routes.js
• Fix prettier PR @ Prettier apply #333

Also see:
TerriaJS/terriajs-server#106

[soyarsauce]

OK @kring this is ready now, I don't know if we want travis to attempt prerendering as part of the build or just skip it for CI:

• on one hand it's actually a good way for CI to catch if the build actually serves up an app that doesn't error out (e.g. it will wait forever if broken, which is what happened while I was tinkering with it and didn't realise I was building a JS-broken-build)
• & on the other hand it will make builds long for big catalog items, or even bail out as it doesn't render any logging out while it's running through all the routes

Working CI test can be seen @ #349 - the only material difference is pointing to the right terriajs commit in package.json
(The timeout param didn't seem to have an effect)

[soyarsauce]

Actually now index.html gets updated as part of the render-datasource-templates gulp task, should we remove this from source to avoid confusion?

[AnaBelgun]

to redev/review after mobx