Provide a better handling of Http connection

Whenever too many request are done concurrently, the http client hangs and wait for a current request to finish before continuing.
This can lead to deadlock on some situation, preventing scenarios such as following an user the current server.

We augmented the pool of connection with XAP-25 to handle this as a short term solution, but we should provide a better way of handling it.

I propose to switch from commons-httpclient to a alternative library build for the cloud and that exploit modern and lightweight IO and concurrency mechanisms (see https://dzone.com/articles/high-concurrency-http-clients-on-the-jvm).