Record Saving

Each ESM/P record struct has a load function (see components/esm). We also need to give them a save function (it can work with a basic std::ostream instead of an equivalent to the ESM reader).

(RM-160 from redmine: created on 2011-08-06 by Lukasz Gromanowski, , closed on 2012-10-01 by Artem Kotsynyak)