This allows users to specify multiple icons like
-i app_res1.png -i app_res2.png -i [...]
linuxdeploy can sort them into the right directory structure, and
their name will be equal to the app name (which is most likely equal
to the Icon entry in the desktop file).
There's two ways to do this:
- either place an AppRun in the AppDir before calling linuxdeploy
- or use the new --custom-apprun parameter
Also fixes a small naming inconsisteny in the info messages.