epmem save/load quickstart

To activate epmem in a context where you want to keep the episodes across Soar runs, do these commands in order:
`epmem --on`
`epmem --set append on`
`epmem --set path <path to file>.db`
`epmem --set database file`

Would be good to put these in the manual or somewhere on the website as an epmem quickstart.