Error handler: Only die if error reporting includes level raised

Normally the error reporting level is set to E_ALL but we may wish to call functions that can raise E_NOTICE in which case we can, after this commit, lower the error reporting and not have our program die.
Account for unserialize() failing

If the data is truncated, for exaple if the server crashes while writing data to disk, then unserialize() will raise E_NOTICE and return FALSE.

We need to change the error reporting so that raising E_NOTICE does not prematurely terminate our program (relies on prior commit).