Tidy up "pkg_mgr_install.php" XHTML

Add start and TR tags
Tidy up the TABLE tag, move height and colspacing in to STYLE paramenter
Update TD tag with correct background syntax
Move end BODY and end HTML tags to the end of the file, this helps
reduce the error count.
Merge pull request #536 from ExolonDX/branch_01

Tidy up "pkg_mgr_install.php" XHTML