Invoke nodemon via grunt when starting server.js during development

Also watch server.js explicitly to avoid suprious restarts.
Fixed a typo
Remove APPCACHE_ENABLED config settings; enable appcache at all times
Rework build process to get accurate source maps

The previous approach involved concatenating pre-minified files for
third-party libs, such as Angular. This was fast and convenient, but
the minified files each reference a corresponding source
map. Concatenation resulted in a file with multiple source map urls.

Instead, minify at build time. This produces a single source
map. Build libs separately from the application, and only rebuild the
application file via watch so that build times remain prompt.

Also, skip file versioning and rely on appcache updates to pull down
updated versions. This makes it much easier to build the application
separately from its libs.