refactor CSS and HTML of labels for asset-info edits

As part of the ongoing saga for CSS of the new core one of the most resistant issue is that some check-boxes' and radio buttons label appear bold (notably the levels in asset-edits). This is due to the rule that was always there that says that a text inside a label element should be made bold.

In curriki till 1.10, this meant just the section titles (e.g. the Levels title).
From curriki 1.11, the core, itself (namely, document.display) includes a label for checkbox which has the advantage that one can click on the text to check the box.

• The CSS rule (in wiki.css) should be restricted to labels of a particular class (input-row-title?)
• The places where this occurs should be found (everywhere with a label in the title?) and the additional class should be written there
• One should check that no-other effect is caused by that change. Among others, the usage of the label element has made MSIE prevent clicks on the TOS link at registration.