Concat all JS files into a single file for prod build

[mcalthrop]

Modify the build process so that for a prod build:

• all JS files, including library files, are concatenated into a single file
• this is included conditionally in index.html when the build is a prod build

And for a dev build:

• index.html includes remain as they are, conditional on the build being a dev one

[mcalthrop]

Hmmm... after trying for a couple of hours, I haven't yet found a solution.

Have tried using the grunt-contrib-concat package, but with no joy; keep getting this JS console error:

Uncaught Error: [$injector:modulerr] Failed to instantiate module MainApp due to:

I tried adding the files in question (ie, all the Angular includes) to the ngmin module, but got the same result.

Leaving it for now.