Support Conduit application of most CustomField transactions in EditEngine

Summary:
Ref T9132. Give most standard custom fields reasonable Conduit support so you can use the new application.x endpoints to set them.

Major missing field type is dates, again.

Test Plan: Used Conduit to set various custom fields on a package.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9132

Differential Revision: https://secure.phabricator.com/D14635