custom dispatcher for sharedClient to allow for more parallel requests

[brintal]

Since commit bed23c0
there is only one application wide shared HTTP client instance.

Because of the fact that no custom dispatcher for this client is configured, the following default request limits apply to the whole application:

  private int maxRequests = 64;
  private int maxRequestsPerHost = 5;

These limits are far to little when running a bigger trading application which retrieves updates for many symbols in parallel.

To solve this issue I introduced a customized dispatcher with maxRequests and maxRequestsPerHost of 500.

[joaopsilva]

Looks good to me, thanks.