Nextcloud SingleSignOn 0.5.0 RC4

#128 SSO: return response headers
#129 throw exception if SSO import is cancelled
#166 Multipart integration
#163 add more debugging output / destroy api when reconnect fails

❗ Breaking changes ❗

• AccountImporter now throws AccountImportCancelledException to inform if import process was cancelled by user, so that 3rd party apps can handle it correctly
• @NonNull Annotation for NextcloudAPI and NetworkRequest

❗ Announcement ❗

• performNextcloudRequestAndBodyStreamV2
• performNextcloudRequestV2
  were introduced, those return a Response object, which contains Inputstream (as known) and headers, so that e.g. eTag can be used
  This deprecates these old methods:
• performNextcloudRequestAndBodyStream
• performNextcloudRequest

These will be deleted in upcoming 0.6.0 release, so please adjust your app