Introduce getter and setter to handle single values

[henryruhs]

Needed helpers:

• getParam
• setParam
• getHeader
• setHeader

Example for setting a single parameter;

public setParam(name: string, value: string): this
{
    return this.setParams(
        this.getParams().set(name, value)
    );
   return this;
}

[henryruhs]

Done