Implement Google Closure Javascript minifier as a part of production run

[MTDdk]

At first it could be a part of the Gradle build, or a simple script.

It should somehow automatically do optimisations when running in production mode.
Most conveniently during bootstrap.
This involves some renaming of referenced scripts by the framework.

Each script referenced in site.json that is locally referred, is prone to this sort of optimising.
Of course this either means, that bootstrap should read all site.json and do this optimisation, OR optimisation will be done dynamically whenever a new site.json is read from disk.

Perhaps let any errors be output as a file next to the .js (either next to the original or the generated), instead of failing the entire build.
Could also output to log during bootstrap.

https://github.com/google/closure-compiler