*header.php files need updated first_run checks (also, not branding-independent)

The generic header.php still uses the old first_run catch of checking for the ./install directory. This must be updated to use the meta table check, in order for it to run properly.

Secondly, the current meta table check in index.php needs to be moved to header.php. This enables first_run checks for ANY page, eliminating the problem of allowing incorrectly configured installations to still run by bypassing /index.php.

Thirdly, the other *header.php files need similar checks. They still use the old $logo variable from the config file, which was deprecated over 20 revisions ago!!!