Tidy up "system_groupmanager.php" XHTML

Add CDATA sections to SCRIPT tags
Close INPUT and BR tags
Update HTML boolean operators
Deprecate the ampersand in ANCHOR tags
Move NOWRAP into class statement
Move TFOOT between the THEAD and TBODY tags, this is a "quirck" of HTML
Move closing BODY tag after "fend.inc"
Add missing closing HTML tag
Merge pull request #540 from ExolonDX/branch_05

Tidy up "system_groupmanager.php" XHTML