Stable high-level client interface

It would be good to have some kind of a stable high-level interface for the QLS clients.
Something that separates concerns and does not change too much over the time.
(an example on lower-levels would be syscalls in Linux).

To illustrate the problem, here would be one example:

• QLS 3.3.2 daemon is installed and running properly on a system
• a client ships with QLS 3.4.0 daemon and has to install it
• the client has to register the daemon (qtlicd.exe --register)
• the client has to figure out whether an update of qtlicd.ini is needed or not
• if needed, it has to run qtlicensetool.exe --migrate-settings
  here it needs to know which keys need update, etc

Each client (in different products) would have to do the same, and QLS is becoming
a moving target from the client point of view.

Maybe we could introduce a simple interface (call to a program/tool, have some libs, or so)
that specifies a minimum amount of information that client has to provide during installation
and the usage to QLS. QLS tools (and libs) would then take care of the rest.

This might be helpful not just for the clients but maybe also for QLS development.