Vagrant: Support host IO cache on SATA, and, optionaly, SSD-aware features

Host IO cache: trade IO speed for security on e.g. host power failure,
more here: https://www.virtualbox.org/manual/ch05.html#iocaching.

`--nonrotational` (optional): This switch allows to enable the
non-rotational flag for virtual hard disks. Some guests (i.e.
Windows 7+) treat such disks like SSDs and don't perform disk
fragmentation on such media.

`--discard` (not implemented): This switch enables the auto-discard
feature for the virtual hard disks. This specifies that a VDI image
will be shrunk in response to the trim command from the guest OS.

https://www.virtualbox.org/manual/ch08.html#vboxmanage-storageattach