Have AttachmentProcessor create Maester Attachments by default

[jhorbulyk]

Migration to Use New API Features

Description

Follow up to #42

The rollout strategy is as follows:

1. Apply Extend AttachmentProcessor so that it can read Maester Attachments #42 so that Maester attachments can be read along side Stewart attachments.
2. Migrate all components that use attachments to this version of the component commons
3. Apply this change so that Maester attachments are used by default.
4. Deprecate Stewart

After this change, only Maester attachments should be created with AttachmentProcessor.