Issue #21: Added fix for upgrade error and added setType for form elemen...

I got the following error message when upgrading with the latest code:

```
Unknown error upgrading mod_adaptivequiz to version 2014050800, can not continue.
```
The file db/upgrade.php expects the standard *return true* statement at the end of the upgrade function. That fixes it.

Also I've added a fix for a notice message when developer debugging is enabled in Moodle that *setType* must be set on a form element.