Add a option to use field name for setters.

[Bin Lan]

As a developer, I would like to avoid using generic name like val or value for setter parameter names. I would like to be able to pass in the parameter using actual field name. E.g.

public Builder withFieldName(String fieldName) {
    this.fieldName = fieldName;
    return this;
}

[Bin Lan]

Also, the prepare-build.sh's download url is outdated.