A simple shortcode that displays the “Total” filed value from any Gravity Form. Parameters * form_id * field_id * start_date * end_date Examples: * [gravityform-total-amount] * [gravityform-total-amount form_id="14"] * [gravityform-total-amount form_id="14" field_id="18"] * [gravityform-total-amount form_id="14" field_id="18" stat_date="2017-07-18"] * [gravityform-total-amount form_id="14" field_id="18" stat_date="2017-07-18" end_date="2017-07-20"]