Display custom content-type content bodies in Network Display

See issue [#153 Network details doesn't display custom content-type body](https://github.com/operasoftware/dragonfly/issues/153)

I also noticed that some content bodies were displayed starting as `data:application/json;base64,` and then followed by the encoded content. I added in the potential base64 decoding prior to the display in the view as well.

I wasn't sure what the policy was on unit test suite maintenance, so I have not submitted my unit tests in this pull request.

Please let me know if this feature is already completed, in-progress, or acceptable in this form :)