Add import aliasing for templates

[callanb]

When working with a structured project layout, you sometimes end up with templates that sit within many sub directories. This means when you want to reference another template, you end up with a long line like @template.path.to.a.far.away.place()

Adding a mechanism to import and alias another template so it can be used in a more terse manner might be a nice solution to this.

If there is already a nice approach / workarounds to this I'd love to hear.

Thanks