Added functions for searching for films and getting their credits

I may end up moving this logic into `api.php`, but just in case I don't, below is some sample code for how to parse the output from `tmdb_film_search()`:

```
$number_of_results = count($results["results"]);

echo "Number of results: " . count($results["results"]) . "</br></br>";

for( $i=0; $i<$number_of_results; $i++ )
{
    echo $results["results"][$i]["id"] . "</br>";
}
```