Issue170 swid measurement controller

Issues:
- Tests depend on bug fix in utils: https://github.com/tnc-ba/strongTNC/pull/187
- We dont save the software-id in the datebase and django unfortunately does not allow to apply filtring based on a model method. This makes querying for matching software-ids troublesome. Is there a better way to do this?
- There seems to be a lot of magic in the autorouting stuff of DRF. I am really not shure where to put this controller. Maybe you can come up with a better solution?

controller can be tested with the following command: 
````
curl -i -X POST http://localhost:8000/api/sessions/2/swid_measurement/ -H "Content-Type: application/json" -d '["regid.2004-03.org.strongswan_debian_7.4-x86_64-strongswan-4.5.2-1.5+deb7u3"]' -u root:root
```
(The "regid.2004-03.org.strongswan_debian_7.4-x86_64-strongswan-4.5.2-1.5+deb7u3" software-id is existing in our repo db.)