Canvas Servlet 404 Scenario

In CanvasServlet.java...
```
if (folioID > 0) {
//Respond with 200
}
else{
//Respond with 404
}
```

This is somewhat off the mark. http://localhost:8080/TPEN/canvas/011100010101 returns a 200, but there is no folio with id `011100010101`

The response code should be better, like
```
if (folioID > 0) {
if(folio exists with this id){
//respond with 200
}
else{
//respond with 404
}
}
else{
// There is no folio with a negative id, or 0, or null id. so 404
}
```