HTML and PHP code cleanup.

• Reduced number of times we drop in and out of <?php ?> mode to
  avoid whitespace created in the output. (And maybe speed up
  parsing?)
• Standardized table cell creation a little
• Removed whitespace in output
• removed class="center" and made center default alignment, since
  its used in all but 2/3 columns in the list

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2561 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9