Add infrastructure for saving WiredTiger metadata in it's own table.

This will lead to us using logical names for tables and indexes, rather
than the MongoDB names.
Switch collections to using explicit metadata.
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' into metadata-table
Fixup name generating in WiredTiger metadata mapping.
Fixup build warnings and add missing file.
More switching WiredTiger to using a separate metadata table.

Still not ready for merging.
Only return indexes in index search.
Merge branch 'master' into metadata-table

Conflicts:
	src/mongo/db/storage/wiredtiger/SConscript
Add wiredtiger_metadata back into build.
Cleanup failed drops in WiredTiger
Fix a hang. Index collation requires the metadata keep configuration information.
Fix an issue renaming an index, when the index existed from an old collection.

This fixes core/mr1.js
It doesn't feel at all right - the default index should be dropped when the
collection is dropped (I think).
Merge pull request #11 from wiredtiger/metadata-table

Keep the metadata in an explicit table, not embedded in the WiredTiger metadata.

Move to using logical rename operations, and don't error if drop fails, remember and retry later.