Make table headers optional when table is empty

[greg-1-anderson]

Overview

This pull request:

• [ ] Fixes a bug
• [x] Adds a feature
• [ ] Breaks backwards compatibility
• [x] Has tests that cover changes

Summary

Add TABLE_EMPTY_MESSAGE formatter option to allow caller to control whether or not table headers should be emitted when the table is empty.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.97%. Comparing base (f65524e) to head (d2557c1). Report is 3 commits behind head on 4.x.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 4.x #108 +/- ## ============================================ + Coverage 91.94% 91.97% +0.03% - Complexity 525 534 +9 ============================================ Files 50 50 Lines 1316 1334 +18 ============================================ + Hits 1210 1227 +17 - Misses 106 107 +1 ```

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