Add test for command 'update'

Command 'update' will update the packages listed in command line. If essential update is found, only essential component will be updated.

Usage: <maintenancetool.exe> update <package> <package>

For succesfull update the following lines appear in log:

"Update finished!"
"Components updated successfully."

If no update are found:

"No updates available."

Make also sure no extra packages are added or removed and only selected packages will be updated.