Import script for Nodewords settings

Here's a patch that adds an update script and site_verify_import_nodewords() for converting the Nodewords settings.

A slight tweak, remove the Nodewords setting regardless of whether or not it was valid, e.g. for blank strings.

Another slight adjustment, run the function during module installation.

Another update, this time includes the Yandex tag.

Small bugfix for a syntax error in the DELETE query.

Hopefully one last patch, fixes a bug in one of the queries.

FYI this is related to the following Nodewords issue: #1028086: Remove search engine verification, promote separate module

Needs a little more work, Nodewords was able to compile the required meta tag based on just a small string whereas Site_Verify needs the full meta tag to be pasted into the string.

Ok, now it creates a simple meta tag in the format:
<meta name="{$tag}" value="{$string}" />