Convert map to http params

map.js

mapToHttpParams(params)
function mapToHttpParams (m : Map) : String {
	let s = "";
	if (!empty(m)) {
		for(let key in m) {
			let value = m[key];
			if (!empty(value)) {
				s = StringUtils.format("{0}{1}{2}={3}", 
					s,
					(s.length != 0) ? "&":"",
					key,
					value );
			}
		}
	}
	
	return s;
}