Load ivil xml schema validate against xsd

I had issues with burp2ivil and load_ivil with malformed files, also reported as https://github.com/schubergphilis/Seccubus_v2/issues/103 . Picked it up and now it validates the xml against an .xsd (located in /SeccubusV2/seccubus.xsd).

The provided "bad" xml now fails as follows:

![image](https://cloud.githubusercontent.com/assets/1157977/3028384/b3e87246-e02b-11e3-9a6a-e43b3dbc4c07.png)