rescue analysis errors in validations
log to current directory by default, not /var/tmp...
set magic attribute to nil if analyser blows up (and log)
no need to complicate meta and url_attributes by adding magic attributes to meta, especially now that we have analyser_cache, etc.
log if validation fails due to exception
Added model to irbrc for local testing
Attachment#add_meta
allow adding a url_path_prefix for getting around SCRIPT_NAME problems