Merge snippets between theme and basetheme

- Current theme has preference over the base theme
- Snippets with the same name are overwritten by the current theme.
- If the overwritten snippet has no `gen` property (or `gen` is falsy), it will remove the base Theme snippet.
- Snippets not overwritten will carry over from base Theme
- New snippets will be added on to base Theme

themes/V3/5eDMG/snippets.js

@@ -21,7 +21,7 @@ module.exports = [
 			{
 				name : 'Column Break',
 				icon : 'fas fa-columns',
-				gen  : '\n\\column\n'
+				gen  : false
 			},
 			{
 				name : 'New Page',