make number of parallel HTTP connections configurable #26

I would like to configure the number of pooled connections in the PoolingHttpClientConnectionManager. The following methods are responsible for that: setMaxTotal, setDefaultMaxPerRoute. Or setMaxPerRoute for the connection to TempoDB.

So maybe the client should have a method setNumberOfParallelConnections that subsequently invokes the methods httpClient.connectionManager.setMaxTotal and one of the other too.

I just mentioned that in the hangout we had.