fix logic error with search filter.

if a post was in more than one different level, it would be hidden from search from ALL levels because the original query would ALWAYS return its ID since it's page_id would exist for a level other that the current user's level.

this update adds a second query to find the posts that ARE in the current users level and subtracts that from the original query.
Added en_GB translations. These change "billing state" to "billing
county". UK WordPress just need to set their WordPress lang to en_GB.

* languages/pmpro-en_GB.mo:
Updated version number.
GitHub contributions.
* Fix to code that hides posts from search to NOT hide posts that a user has access to but might also be accessible by users of a different level. (Thanks, normanyung on GitHub)
* Added a pmpro-en_GB translation that changes "State" to "County" on the billing address fields. (Thanks, alexbiddle on GitHub)
Update Stripe Gateway Class (Customer Description)

If the order has a first/last name associated with it, use that,
otherwise, use the first/last name from the user meta.
Update Stripe Gateway Class (Customer Description)
Fixed bug where "Show Billing Fields" option for Stripe was sometimes hidden on the payment settings page.
hooks for adding column to table view

Added hook pmpro_discountcodes_extra_cols_header and pmpro_discountcodes_extra_cols_body to add new column to discountcodes admin page view
Update discountcodes.php
* Added hooks.
* Updated the expiration field dropdown on the edit levels page to use translation strings. (Thanks, 24uurdates)
Added the pmpro_member_startdate filter to filter the pmpro_getMemberStartdate function. Passes $user_id, and $level_id as parameters.