Summary:
Adds a new test for formatting and fix several related bugs it uncovered:
1. When editing a number with "," decimal separator, ensure it opens in
the editor with "," (rather than ".", the original bug motivating this).
2. When guessing number format, set maxDecimals when it's needed
(otherwise, e.g. "$1.234", or "4.5%" weren't guessed as numeric)
3. When guessing number format, ignore whitespace when deciding if
guessed format is correct (otherwise percents can't be guessed in
locales which add "%" with a non-breaking space before it).
Test Plan: Added a test case that exercises all fixed behaviors.
Reviewers: paulfitz
Reviewed By: paulfitz
Subscribers: paulfitz
Differential Revision: https://phab.getgrist.com/D4177
