Gather more aggregated information

[dzzh]

So far daemon mostly works with the requests and response codes, but log files contain way more useful information, that can be aggregated and monitored, e.g. average and total number of sent bytes. Think on what useful data can be retrieved, how to abstract parsing these data and build pluggable modules for its retrieval.

[dzzh]

It is needed to re-think the architecture a little bit and move parsing code to separate plugins that can be enabled and disabled. Also, the plugins should be able to define and use own storages.