Make Annotation's serializable and initial implementation of adding annotations to the Exporter output

[lewismc]

Hi @jnioche ,
Please see the patch below which does the following

• makes Annotation’s serializable, meaning we can export them alongside document text as either binary or textual content.
• implements the command line boolean flag for facilitating the above
• implements the core logic for exporting Annotations as string values, comma separated
• concatenates both textual content and annotations, then deep clones the object and returns it for exporting.

An issue is that the concatenation is not a join.
What do you think about the patch. Is it worthy of inclusion into Behemoth?

[jnioche]

Hi @lewismc - will have a closer look when coming back from holiday. Thanks

[lewismc]

Enjoy holidays @jnioche safe travels