@michaelcahill, this is a pass through the list of configuration options, doing additional configuration checks.

Along the way I merged the btree and log compressor lookup code and added checks for empty or "none" collator, compressor and extractor values to the underlying functions to guarantee it gets done.

I would have liked to have created an underlying collator function that handles the collator's associated metadata lookup, but the 5 or so places we do that work are subtly different.

I skipped the columns, source, type, colgroups and extensions configuration strings, I didn't see any obvious way to validate them – if you can think of something useful we can do there, let me know.

Reference WT-1755.