implement multi-table INSERT statement

[sjhewitt]

1. What GitHub issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes #403

2. Fill out the following pre-review checklist:

   • [x] I am adding a new automated test(s) to verify correctness of my new code
   • [ ] I am adding new logging messages
   • [ ] I am adding new credentials
   • [ ] I am adding a new dependency

3. Please describe how your code solves the related issue.

This adds the InsertMulti class to handle composing and rendering the INSERT ALL/FIRST clause