fail gracefully when a schema lookup fails do to import error in lookupSchema
merge latest
Merge pull request #15 from eleddy/missing_files_patch

Gracefully handle missing schema lookups
Zap gremlins.
Preparing release 2.1.3
consistency with archetypes
fix: encoded string for Creator accessor (CMF)
doc: upgrade guide
add support for GS content import/export
keep Containers from acting as folders when they aren't allowed to contain any types
use a different filename so we don't collide with CMF which expects a different format
remove dependency on CMFDefault
revert fancy isPrincipiaFolderish logic, it doesn't work
we sometimes have latin-1 here
merge in latest for 2.2.0