Allow silent install without application launch

[stschulte]

Some users may want to install moolticute in an unattended silent way, e.g. the following installs in silent mode skipping the creation of a desktop icon:

setupfile.exe /VERYSILENT /TASKS="!desktopicon"

However this will still run programs in the RUN section which executes moolticute. This is undesired in an unattended setup, so we skip this on silent installs.

NOTE: My change is based on the innosetup documentation but I did not run a build myself off this commit since I have no prior experience with innosetup.