search.html: Make the search input a function GET form

Issue #119.
lib: Add a _GET superglobals API

Issue #119.
results.php: Set search_text from query

Issue #119.
results.php: Return results that match query

Issue #119.
results.php: Use existing variable

Issue #119.
_navbar.html: Match _GET variable with search form

Issue #119.
results.php: Only set results if some were found

Issue #119.
results.php: Set result count properly

Issue #119.