get.php: Add query GET variables

Issue #146.
lib: Add a Pip_Query class

This class provides a representation of a query.

Issue #146.
lib: Refactor Links into an associative array

This allows for other types of links, such as images, JavaScript, etc.

Issue #146.
advanced.html: Assign ID to advanced form

Issue #146.
advanced.html: Give a default dropdown option

Issue #146.
Add an advanced search JavaScript front-end

Issue #146.
Merge branch 'feature/146'