ExampleWidget sample page improvements, refs #236
Handlebars: better handling for duplicate bind variables.

For example, expressions like "Hello {{name}}.  How are you {{name}}?"
or {{this.x < 0 ? Infinity : this.x}}.

In this case, generate an if() like if("name" in props) rather than
if("name" in props || "name" in props).
fix templates build
remove requirejs-text dependency