feat: Changes to io

Keyword "io" now has many more usage scenarios.

- Default margin for io now 0
- New config value for inline element margin
- Rename first classes
- Io classes integrated to sections and groups

elements/_interactive.scss

@@ -57,7 +57,7 @@ label + input {
 }
 
 input, button, textarea, select {
-	margin: $margin_io;
+	margin: $margin_inline;
 
 	&[disabled="disabled"],
 	&[disabled] {
@@ -79,6 +79,10 @@ td > textarea {
 	}
 }
 
+.input_io, .button_io, .io_textarea, .io_select {
+	margin: $margin_io;
+}
+
 .input_io, .io_textarea, .io_select {
 	padding: $space_half;
 	color: $color_text_io;