This commit introduces a "visited files" list that contains all files
that have already been processed by the deployment operations.
This is similar to the visited node lists many routing algorithms use,
e.g., Dijkstra and its derivatives like A*.
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.