Update JSON serialization methods for Gramps 6.0

[DavidMStraub]

@dsblank would you mind summarizing briefly the changes made in gramps-project/gramps#1876 to Gramps core?

Gramps Web API uses the existing gramps.gen.lib.serialize which has been removed, so it will be some work changing it.

[dsblank]

Can you point to an example in the gramps-web-api that uses the methods? I don't mind doing the update myself.

BTW, gramps.gen.lib.serialize hasn't been removed, and all of the functions are still there (renamed) if you have a DB instance. Otherwise, you can use the underlying methods in gramps.gen.lib.json_utils.

[DavidMStraub]

Thanks!

Here are some examples:

• UndoDb https://github.com/gramps-project/gramps-web-api/blob/master/gramps_webapi/undodb.py#L82-L93
• Transactions as JSON https://github.com/gramps-project/gramps-web-api/blob/master/gramps_webapi/undodb.py#L82-L93
• Parsing JSON objects https://github.com/gramps-project/gramps-web-api/blob/master/gramps_webapi/api/resources/base.py#L152-L167

[dsblank]

Thanks! I'll start a PR. From what I've seen, these bits should run faster.