Fix SOAP fault parsing

Currently, when an HTTP 500 is returned, an exception is raised about a missing SOAP header. This is because SOAP faults from EWS don't contain headers. Instead of trying to parse the SOAP message the web existing exception handling logic should be called here.

I also cleaned up the `ServiceRequestBase` related classes a little bit, before the fix could be done.
IntelliJ IDEA orders `javax.*` imports before `java.*` imports by default. I'm not sure we want to change this as long as the coding standards for this project are undefined.

![intellij-import-defaults](https://cloud.githubusercontent.com/assets/3531885/4121223/5ef86346-32b9-11e4-9def-97c6170fc293.png)