Refactored search.php from dist-php to demos-php

I've factored the search.php files out of the dist-php folder. I found with my own site that I couldn't implement the custom search for my site with out modifying the search.php files in the dist folders. Meaning that when a PHP update comes down the line and I drop in a new PHP version to replace my current dist-php folder with a newer one, I'll have to redo the custom search.

All the dist-php/{theme}/cont/head-nav.php files include the /dist-php/inc/search.php file, which will include the /demos-php/search/{theme}/search.php file or will include the file the user specifies with the $_SITE['wb_search_file'] variable in their sites custom config.php file.

If deemed an acceptable solution, I'll add documentation to the PHP wiki describing how to use the /demos-php/search/{theme}/search.php files as templates for a sites custom search.