Now using view->fopen() to stream file contents to clamav

- Now always streaming the file's contents to clamav
- Fixes #1384 where a user uploads a file to a read-write shared dir
- Fixes case with encryption enabled
- Refactored socket connection with daemon connection approach (and
  removed the lib dependency)
Use storage to unlink the virus file
Merge pull request #1447 from owncloud/antivirus-viewfopenstream

Now using view->fopen() to stream file contents to clamav