* Fix layout of the topic edit.
- made right-hand column wider so that it has enough space for "Done" button.
- fixed issue that jQuery's .show() breaks functionality of the Semantic UI Grid.
* Improve switching visibility of the topic edit
Changes to support old browsers that doesn't support 'flex' keyword.
- Removed style "display: none" from index.css so that
the grid can be displayed without specifying new "display" style.
- Added style "display:none" to the grid element in HTML template
as the initial style.
- In index.js, visibility of the grid element is changed by
set "display:none" style to the element or removing it from the element.
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