Modified searchFilter to scope exclusion to public search only.

Hi Roman,
In reference to the following:

https://wordpress.org/support/topic/scope-exclude-to-ignore-admin-searches?replies=2#post-5692569 

I have created a fork of your search exclude plugin and made the changes I mentioned in the post above on a new branch here. Please take a look and advise as needed. If you think it's worth adding to the official plugin I would be honored! :)

Cheers,
-WD