Added support for deleting >500 entities

• delete_multi allows you to delete > 500 entities in chunks of a customizable size, defaulting to size 500.

Ability to exclude properties from index

• Certain properties can now be prevented from being indexed. Google Datastore indexes all columns automatically which can give problems when large arrays are used as column values.

Fixed dependency versions

fixed dependency versions to avoid problems with breaking changes

Allowed to specify encoding of BytesField

• Sometimes the encoding of BytesField may differ, now this can be specified.

fix put over 500

• put_multi now auto-batches puts in batches of 500, putting more than 500 elements was previously not possible.
• The same goes for get_multi except the batch size is 1000.

hotfix

Fixed calling the wrong method when deserializing

fixed dot in property name

Dots are not allowed in property names in the datastore, this release adds a custom DictField that automatically replaces all '.' in property names with '[dot]'.