ModuleImport: Handle failures and edge cases

[partipan-dot]

The ModuleImporter is very naively implemented. It hopes the import succeeds always. The importModule(...) catches IOExceptions and returns null which lead to a NullPointerException in the AsyncTask. The exceptions get logged but the user only sees that the app crashed.

Problems:

• Check if module imported correctly in AsyncTask iterating over the result (null -> NullPointerException)
• During import the module lies in a tmp_extraction folder which get renamed afterwards (don't ignore result, it can fail)
• Handle low space or no space
• ManifestParser can't handle missing/unknown json attributes (app crashes)
• The zip can be corrupted or not a zip at all
• Expected files can be missing in zip
• Notify user that something went wrong (be specific but user friendy)