MEDIUM: log/balance: support for the "hash" lb algorithm

MEDIUM: log/balance: support for the "hash" lb algorithm

hash lb algorithm can be configured with the "log-balance hash <cnv_list>"
directive. With this algorithm, the user specifies a converter list with
<cnv_list>.

The produced log message will be passed as-is to the provided converter
list, and the resulting hash will be used to select the log server that
will receive the log message.