RemotePermissions: Store in a class rather than in a QByteArray to save memory

RemotePermissions: Store in a class rather than in a QByteArray to save memory

Create a specific type that parses the permissions so we can store
it in a short rather than in a QByteArray

Note: in RemotePermissions::toString, we make sure the string is not
empty by adding a space, this was already existing before commit
e8f7adc7cacd4f55e26b2dd14464654e82204307 where it was removed by mistake.