Uglify name mangling breaks qmlweb

[Plaristote]

The minimized built qmlweb.min.js doesn't work, since registerQmlType relies on constructor names.

I've been able to build qmlweb with proper minimization options using the command-line Uglifyjs tool. Basically, we just run it bare, zero options, and it works.

I haven't been able to reach the same result using Gulp. I should supposedly send the {mangle: false} option, but that doesn't seem to change anything.