rename $g_summary_product_colon_category to $g_summary_category_include_project

The name was confusing because it referred to 'product' instead of 'project' and the 'colon' portion seemed odd. I added an entry to obsolete.php in case anyone is already using this (the original option is only in CVS code, not in any release)

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1662 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9