Topic/ceph

Hi,

Please review my fixes for "topic/ceph" branch.

I've found that you updated Ceph broker sources to support new libcephfs, but I suppose you didn't test it yet. There are several bugs.

* CephBroker.Id and CephBroker.RootDir properties aren't declared in Hypertable config and thus CephBroker doesn't start. 
* You are calling ceph_read and ceph_write with offset 0 that means read/write at position 0, but not read/wrire at current position, which is expected for CephBroker::append and CephBroker::read.