- added small non-yet-working work-around

the ZODB_BLOB_TEMPDIR environment variable.  We don't use a value from ZConfig
because ZConfig use isn't mandated for standalone ZODB usage.

 - made ClientStorage and BlobStorage create the blob root directories automatically

 - replaced "DIRTY" with "LOADING" for ClientStorage

 - fixed problem handling data manager registrations for non-default 
   transaction managers

Formatting changes.

- Made the ClientStorage cache directory the same structure as BlobStorage

up on the system. Also add some tests for the configuration of BlobStorage.

Add a test to show that our cleanup code (currently in "_abort") doesn't get called.  The complexity of the proxied storage, the connection as a datamanager, and the transaction indirections make it unclear exactly how to hook a transaction abort for cleanup purposes.

Override tpc_begin and tpc_abort because methods found on the proxied object aren't rebound to the proxy. :-(