Add a DummyInstaller to handle non apk files

• Avoids crashes when trying to treat non apk files, such as privileged extension ota update.zip as apks
• Doesn't do anything at all for now.

One issue with this is the app is always in the not installed state, so what would be appropriate here would be to change the text of the install button to download, and update that accrodingly. However that is outside of the scope of this change.

TODO: Add toast indicating the user that they need to install manually, in case of OTA update.zip

Avoids the crashes in #982 #933 (closed)

Should we add a toast somewhere about the ota update.zip installation?

I think that just this could be fine for %0.103 - UX Overhaul, minimal set of changes to avoid crashes.

Current issue is with this when you try to "install" the ota zip, it will download it and then do nothing. The install button still stays there, but doesn't do anything.

mentioned in issue #933 (closed)

added bazaar label

looks good to me!

changed milestone to %0.103 - UX Overhaul

unmarked as a Work In Progress

merged