Issue#37 Disallow change F2F / Code challenge types in project challenge...

![image](https://cloud.githubusercontent.com/assets/6339380/4848029/49c81f36-6057-11e4-91e0-3f5028cc796b.png)

For other software types, the option code / first2finish are removed to avoid changing to them

![image](https://cloud.githubusercontent.com/assets/6339380/4848046/5eebe0d2-6057-11e4-9825-71c630607d9b.png)