Reorder load.sh

Putting like with like, but also putting the more 'important' data first.
Mappings are more important at least in as much as we run tests against those.
Speed up load.sh by truncating hits/totals data

We use this script to bring in the latest site, host and mapping data from
redirector becuase it is currently the canonical source of mappings. At some
point, the canonical source for that data will be Transition app.

Mappings need to be continuously available, but hits and totals can be missing
if done out-of-hours.

Originally we dropped the database and inserted all the data. This was fast -
~1hr50m. Unfortunately it meant bouncer would stop working properly.

We then tried using 'robust' - updating everything in place. This took 11 hours,
which is too much.

This mixed approach should get reasonable speed without breaking redirects.
Merge pull request #76 from alphagov/speed_up_load_sh

Speed up load sh