Adds option to the settings page so the top folder can be collapsed.

Till now only subfolders could be collapsed, this adds options so the top root folder can be collapsed by default as well.

This will show up in settings:
![settings](https://cloud.githubusercontent.com/assets/1096073/3400628/04a854d4-fd47-11e3-8faf-c66cbff9b6c1.png)

Normaly the root folder would be expanded by default:
![moodle](https://cloud.githubusercontent.com/assets/1096073/3400649/392da218-fd47-11e3-83fb-72606796beed.png)

With this patch it can be setup to be collapsed:
![top](https://cloud.githubusercontent.com/assets/1096073/3400657/53a09be6-fd47-11e3-8b09-33034a69d48e.png)