Tidy up "services_captiveportal.php" XHTML

Add "closehead" variable, move script into HEAD and close head manually
Add CDATA sections to SCRIPT
Add SUMMARY to tables
Update HTML Boolean Operators
Close INPUT
Remove duplicate closing TR
Add opening TR
Add closing TD
Change "_new" to "_blank" in anchor tag
Merge pull request #1047 from ExolonDX/branch_master_03

Tidy up "services_captiveportal.php" XHTML