have DocumentSchema use jsonobject

deletes a ton of code whose functionality has moved to jsonobject
fix save
use jsonobject.exceptions.BadValueError
use exclude_if_none instead of removing from doc in to_json()
remove support for clone()
use _validate_lazily
change tests i do not like
use jsonobject SetProperty
rename _validate_lazily to _validate_required_lazily
fix DocumentBase.save
use jsonobject's DecimalProperty and TimeProperty
fix ProxyDict
remove support for creating schemas as instances of DocumentSchema
remove support for using schema instance as item_type
change error message expected in test
finish fixing a test
change tests to expect validate to return None
change tests to expect adding the wrong type of element to a typed container to fail fast

raises BadValueError
change tests to expect containers to normalize their values eagerly
expose ALLOWED_PROPERTY_TYPES back