annotator.config.settings currently exports an object containing
individual standalone functions for returning different settings'
values:

    module.exports = {
      app: appFunction,
      annotations: annotationsFunction,
      ...
    };

Change it to export just a single constructor function - settingsFrom()
- that returns an object containing the previously-exported functions as
methods:

    function settingsFrom(window_) {
      ...
      return {
        get app() { return app(); },
        get annotations() { return annotations(); },
        ...
      };
    }

    module.exports = settingsFrom;

Note that ES5 getters are used so that, even though app() and
annotations() are methods rather than simple properties now, they can
still be accessed as properties - settings.app not settings.app(). This
makes the code that uses this object slightly simpler, and makes mocking
this object in unit tests simpler.

The diff of this commit looks big, because the indentation of a lot of
code is changed, but it really is just changing functions into methods
and not actually changing the code of any of those functions.

The reason for turning functions into an object with methods is so that
the object that settingsFrom() returns can have state (by having closure
variables inside the settingsFrom() function). We don't make any use of
this state yet but future commits will do.