Fix YUI Compressor incompatibilities and improve JavaScript correctness

[easleydp]

Solves #2445

Reason for changes: (1) To allow the Vis distributed code to be processed by YUI Compressor (e.g. via tools such as Sencha Cmd, where it can be difficult not to use a compressor). (2) Improve general JavaScript correctness.

Summary of changes:

1. Changes to Vis application code:
   1.1) Avoid using "boolean" as a variable name because it is a JavaScript reserved word. (Used "bool" instead.)
   1.2) Avoid using "char" as a variable name because it is a JavaScript reserved word. (Used "ch" instead.)

2. Changes to Babel configuration:
   2.1) Include the 'transform-es3-property-literals' Babel plugin to ensure that reserved words are quoted in object property keys, e.g.:
   function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { 'default': obj }; }
   rather than:
   function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
   2.2) Include the 'transform-es3-member-expression-literals' Babel plugin to ensure that reserved words are quoted in property accesses, e.g.:
   return new _Configurator2['default'](this, this.dom.container, configureOptions);
   rather than:
   return new _Configurator2.default(this, this.dom.container, configureOptions);

[yotamberk]

Nice! Thank you!

[eymiha]

I've detailed the problem and solution for issue #2500 as a comment there.