Handle timeout & append_list

The changes I made:
1. coord_fsm returns error message with reason when failure happens, including 
     error of log_vnode, 
     can_not_reach_vnode, which means the coordinator can not reach any vnodes of a replication group
     quorum_unreachable,  when an operation fail because can not get enough reply from quorums
     timeout, when coordinator somehow failed to finish operation within sometime
2. Add different timeout for different operations.
3. Fix indentation problems in my files.
4. Add a riak_test to check some of error messages are actually returned.
My branch also contains the changes made by Manuel in append_list.