* adapted from work by Norman Rzepka at scalable minds

* to check equality agains

* and fix compose method

* if a version exists, avoid checking existance of root

…e; rely on tempWriter infrastructure

* used for debugging

…ly during reader creation

Some backends may either have no concept of a directory, or may not have list permission. Either way, if we can infer the container exists by the existence of attributes first, that is good enough.

have to do a hack to share the cache for the HttpReaderFsWriter, that that's just to ensure the cache is updated on write, which is outside the scope of the HTTPReader