Try harder to cleanup after a failed wiredtiger_open call.

References issue #427
Add a paragraph on cursor persistence to the perf tuning page.
Add tuning advise for os_cache_dirty_max, os_cache_max.
Try and group WT cache options together, add more discussion of compression.
Don't drop core if an open fails, it's just a distraction from debugging.
os_cache_dirty_max, os_cache_max are WT_SESSION::create configuration
flags, not wiredtiger_open.
Make more of ex_all run, I want to test some session configuration strings.
Create/drop the table we're manipulating, otherwise we don't get config
checking on the configuration strings.
Fix a bug where absolute path names URIs were not being parsed correctly

Also adjust the stat file logging name creation to do less allocations.
Minor style change, don't test pointer as if it's a boolean, don't check
if a pointer is NULL before freeing it.
Merge pull request #482 from wiredtiger/open-cleanup

Try harder to cleanup after a failed wiredtiger_open call.
Minor cleanup of the WT_COMPRESSOR docs, list all of the possible structure
members.
Merge branch 'develop' into merge-opt