Log user agents in logplex_logs_rest into at ets table.
Only log user-agents sending to the old hostname.
Create ets tables for legacy input tracking in logplex_db.
Support binary, regex, and integer_list types in cache_os_envvars.
Track usage of legacy hosts in logplex_logs_rest.

Keep bare numbers (legacy vs not) in logplex_stats key, but if
legacy_input_host_gather is set, then also track user-agent counts in
ets. These can be correlated to specific addons with a simple heuristic.