Summary:
This addresses two issues, differently:
- For a formula with leading whitespace, like " 1+1", it is stored as is, but
is fixed to work (it should be valid Python, and whitespace is only stripped out
at parsing time to avoid intentation errors caused by the way it gets parsed)
- For a formula with a leading equals-sign ("="), it is stripped out on the
client side before the formula is stored. Grist documentation uses leading
"=" to indicate formulas (because UI shows an "=" icon), and Excel formulas
actually contain the leading "=", so it is a common mistake to include it.
Test Plan: Added new test cases
Reviewers: jarek
Reviewed By: jarek
Differential Revision: https://phab.getgrist.com/D3873
