osx: update package Welcome message

* drop icarus, freehdl, adms (better use a package manager)
* add only asco
osx: update build package script

* add background, license, welcome,... files
* add postflight script to create symlinks in /Applications
osx: add postinstall scritp

* create symlinks in /Applications
osx: add package customization file
osx: update uninstall qucs pkg script