Statistics cursor reset

@michael, I think this is close to what we need for WT-1533, two questions:

1. I couldn't think of any way to avoid copying the incoming configuration strings when the cursor is opened.

1. I almost made the change to not initialize the cursor when opening it (if we wait until the first operation after cursor-reset to initialize the cursor, might as well wait until the first operation after cursor-open to initialize the cursor), but for some reason, that makes Python sad, I get;

File "/b/bostic/wt.develop/lang/python/wiredtiger/__init__.py", line 337, in __getitem__

raise KeyError

KeyError