Create a portable version of the app

[pvginkel]

This must be a zip file that you can run the app from. When updating, it needs to use a portable version to update itself, and do so in place.

This is to help the roaming profile scenario. People can have their own copy of the binaries somewhere without the need to run the MSI. We need to consider moving the local app data folder into the portable folder, but this may be unexpected or unbearable.

We should allow for a portable.cfg file that marks the app as portable, and give it some settings like "support auto update" and "embed local app data folder". We could also go as far as allowing everything to be contained in the folder with file based replacement for the registry settings.