uwt: fix, cleanup temporary file on exit
whonixcheck: html tags
build script: install whonix-gateway or whonix-workstation meta package respectively
build script: Use SAS rather than SATA as virtual hard disk controller for VirtualBox hdds to work around a VirtualBox upstream bug that causes filesystem corruption on high disk I/O (https://www.virtualbox.org/ticket/10031). Thanks to @Neurodrive for the bug report (https://github.com/Whonix/Whonix/issues/274). Fixed #274.
whonixcheck: fix, clean up temporary directory