Bug Fix for [version 9](https://github.com/ImperialCollegeLondon/covid19model/releases/tag/v9.0) release

Bugfix in post-processing: deprecated temporary directory in save-posterior-samples, a table that was not in a data.table format in post-processing-summarise-antibody.R, files not correctly called if re-run in post-processing-plot-age-newcases.R and incorrect file name spelling in post-processing-etas.R.

Rest everything remains the same as version 9.