Example of showing how to use licensechecker plugin

Licensechecker plugin is a QtCreator plugin which is installer for all
except opensource users. This example shows how to check if user has
evaluation license and how to launch dialog when starting QtCreator to
ask user if he wants to install vplay plugin. For evaluation users it is
not possible to disable the install, only is informed to user that data
is collected. The vplay plugin install itself is not done in this example.
The relevant part for connecting to licensechecker plugin and to launch
dialog is done in vplayplugintestplugin.cpp extensionsInitialized()
-function.