Top level cmake: use static jerasure libraries on cygwin to bild dynamic qfs client, as the jerasure build doesn't produce dynamic libraries on cygwin.
Client library: implement KfsClient constructor with KfsNetClient argument, to allow to setup client with the client state machine. In this mode kfs client does not perform any "automatic/default" global initialization, and will not start protocol worker thread, unless file read or write / append invoked.