Add failing unit tests for issue #1269

- Add test for word forward from entirely blank line
- Add test for word forward from last word of last line
- Fix order of expected vs. actual in related tests
Rewrite motion by word in insert-mode to use motion infrastructure

- Make motion utilities usable by insert utilties
- Use them in MoveCaretByWord instead of word utilities
- Adjust unit test scaffolding for API changes
- Allow insert mode to bypass virtualedit adjustment

Closes #1269.
Merge pull request #1271 from ricksladkey/fixes-1269

Fixes 1269