Introduced Tester.assertInstanceOf method, refs #602

- add utils.betterInstanceOf
- add 12 tests
- add documentation
Improved output of Tester.assertInstanceOf() method
Added documentation for new Utils.betterInstanceOf method()
Fixed syntax and vocabulary on comments relative to betterInstanceOf

- in modules/tester.js
- in modules/utils.js
and BTW in their documentations
Modified .jshintrc to allow weak equality testing
Modified betterInstanceOf to make weak equality
Added eqnull parameter on jshint configuration

Tolerate use of `== null`, see also this
[sample](https://github.com/jshint/jshint/blob/master/examples/.jshintrc)
Disallow enfore === equality in .jshintrc configuration
Fixed syntax on .jshintrc configuration file
Disallow enforce === equality in .jshintrc file
Implemented weak equality for jslint locally

... and BTW removed from global configuration
Added XMLDocument test for betterInstanceOf()

thanks to n1k0
Allowed triple equality for betterInstanceOf()
Tested an implementation to fix jshint issue
Moved precedent commit
Tested an implementation to fix jshint issue
Finaly, fixed jshint issue by @n1k0

Thanks
Added XMLDocument to local scope

on Utils.betterInstanceOf() method
Fixed syntax on jshint annotation
Renamed output variable name

From constructor to constructorName because it's a string which is
returned and not a function