Decrease memory usage of updater This release decreases memory usage of updater during update process about 40%. Memory usage is still not ideal but this improves stuff a lot. There is disadvantage to this change as it increases storage requirements during update from at maximum twice size of all packages (installed version and not yet installed one) to thee times (+download packed files). * pkgupdate now downloads packages to /usr/share/updater/download instead of ram. * pkgupdate now downloads packages only when plan is approved, not before. * Added memory usage test bench