Changed id to alumid everywhere.

Also changed all fields called `id` to `alumid`.

This ensures that there is no confusion between the `userid` field and the `alumid` field.

I have checked this file, and it gets imported into MySql without any problems.

![image](https://cloud.githubusercontent.com/assets/3668034/3677313/4173e8fc-1290-11e4-8e5e-e5f30ac44174.png)