Renders a button that opens a form in a modal dialog via the formmodal() JavaScript function.
BTN_MODAL — set as ReportType in def_report.
def Render(self, Param1="", Param2="", Param3="") -> str:
Param1 encodes the form code and up to four additional parameters separated by ^. Button colour is determined by the third parameter: ON = danger (red), OFF = success (green), MID = warning (yellow), any other value = primary (blue), none = success (green). Icon is chosen from self.Parent._Actionglyph or self.Parent._Dismissglyph for ON/OFF states, or self._Glyph, or defaults to fa-plus (no params) or fa-eye (with params).