Fix vboxwrapper documentation

[AenBleidd]

@computezrmle, please fix documentation to include changes from the next PRs:

• Configure more vram to avoid VMs get stuck during boot #4630
• forward rtc setting from host to guest #4631
• Make sata/IntelAHCI the default virtual disk controller #4632

[computezrmle]

Done.
See: https://boinc.berkeley.edu/trac/wiki/VboxApps

The vboxwrapper version number in the manual needs to be updated when the new version is published.
Can this be done prior to the full release and copied to https://boinc.berkeley.edu/dl/?

The vboxwrapper should be compiled with "--enable-optimize".
As of my experience this helps to avoid the "Postponed ..." complaints that can be seen in different project forums.

[AenBleidd]

The vboxwrapper version number in the manual needs to be updated when the new version is published.
Can this be done prior to the full release and copied to https://boinc.berkeley.edu/dl/?

vboxwrapper releases are not really connected to client/manager release.

@computezrmle, thanks for updating the documentation and for your fixes of vboxwrapper!