Speed up "Saving Application Details" part of repo update

Fixes 506.

This does the thing mentioned in 506 (renaming temp table, rather than copying data). In the process, I also identified that the temp tables were missing key indexes which slowed the process down. This fix took the update time from ~100 seconds to ~60 seconds on my Nexus 4.

Below are a couple of log cats from before and after the change (this logging is not part of this MR, it was just for diagnosing the problem).

Before change:

            AppProvider  D  Calculating whether apps are compatible, based on whether any of their apks are compatible
                         D  Update compatible flags took 20244ms
                         D  Calculating suggested versions for all apps which specify an upstream version code.
                         D  Update suggested from upstream took 17808ms
                         D  Calculating suggested versions for all apps which don't specify an upstream version code.
                         D  Update suggested from latest took 129ms
            AppProvider  D  Update icon URLs took 7879ms
          UpdateService  I  Updating repo(s) complete, took 104 seconds to complete.

After change:

            AppProvider  D  Calculating whether apps are compatible, based on whether any of their apks are compatible
                         D  Update compatible flags took 1047ms
                         D  Calculating suggested versions for all apps which specify an upstream version code.
                         D  Update suggested from upstream took 601ms
                         D  Calculating suggested versions for all apps which don't specify an upstream version code.
                         D  Update suggested from latest took 136ms
                         D  Update icon URLs took 887ms
          UpdateService  I  Updating repo(s) complete, took 63 seconds to complete.