HTML/CSS fixes for bug_report_page.php

Added correct class to fieldset to display "required" legend in footer.
CSS: new 'spacer' class for div

In 1.2.x we used to add a table row with a 'spacer' class to separate
rows in a table.

This commit introduces a new class that can be used in form container
divs to separate field container divs:

Before:
	<table>
		<tr>...</tr>
		<tr class="spacer"></tr>
		<tr>...</tr>
	</table>
Now:
	<div class="form-container">
		<div class="field-container">...</div>
		<div class="field-container spacer">...</div>
	</div>
CSS: added new div width classes

With these, we can adjust the layout like it was in 1.2.x tables.