Giving the possibility to administrators to pre-define session resolution for virtual desktops

In some cases, for example with certain applications which require a specific resolution, administrators need to pre-define the resolution of the NoMachine virtual desktop.  Additionally, having the possibility to define a minimum and a maximum resolution can give more flexibility to cover all those cases in which it's necessary to provide users with the optimal screen resolution.

Fixed, minimum and maximum resolution can be a node configuration, see https://www.nomachine.com/FR09O03515.

The resolutions which are not permitted, will be not displayed in the client menu and in the system menu as well.