User Story

As a developer, I want to change the style for the built in file upload dialog.

Acceptance Criteria

replace hard coded inline-styles with theme specific CSS classes (allowing customization via CSS without changing the default template)

e.g. to also adapt to dark themes

Details

the dialog open when using the Fileupload.get method:

		Map<String, Object> params = new HashMap<>();
		Fileupload.get(params, "Choose a file: ", "Upload files", null, 10, 100, true, event -> { });

as of now it's only possible to change the styling of this dialog by replacing the internal upload dialog template

		Fileupload.setTemplate("myfileuploaddlg.zul");