Eagerly load Blob schema

[isaacabraham]

Related to #66. We currently only load types for blobs as the containing folder is accessed. This can sometimes cause problems (although not as much as with tables) in terms of accessing types that haven't yet been accessed. I wouldn't expect us to automatically eagerly read through all blobs - that could be very expensive - but perhaps reading to a certain depth or being provided with a set of paths to eagerly evaluate could work.