Bugfix to Button; Updated demo scenes

Button.hx
* Set optional arguments in Text constructor to 0 - project can now
compile to Flash / HTML5
* Button ID is set to label text by default
* Updated comments

Label.hx
* Aded newSize argument to constructor - Label text size can be
specified in constructor

DemoScene.hx
* Menu created as array of Button types

TitleScene.hx
* Removed click counter example
* Menu created as array of Button types
Bugfix to Label

Label.hx
* Optional arguments in Text constructor set to 0 - it is now possible
to compile project to Flash/HTML5
Removed unused code