Bug: Can't add FormulaR1C1 referencing sheets with spaces

[canettas]

If the string on FormulaR1C1 contains single quotation marks, to reference sheets with spaces, we get unexpected results.

A nice test is:

using (var pack = new ExcelPackage())
{
//create sheets
var sheet1 = pack.Workbook.Worksheets.Add("Sheet 1");
var sheet2 = pack.Workbook.Worksheets.Add("Sheet 2");
//set some default values
sheet1.Cells[1, 1].Value = 1;
sheet2.Cells[1, 1].Value = 2;
//fill the formula
var formula = string.Format("'{0}'!R1C1", sheet1.Name);
var cell = sheet2.Cells[2, 1];
cell.FormulaR1C1 = formula;

//Formula should remain the same
Assert.AreEqual(formula.ToUpper(), cell.FormulaR1C1.ToUpper());
}

The error was inserted on Commit f481e9d on 2017-12-24; Merged on Commit 97b51ab on 2018-02-04.

The problem is that after the alteration the TokenFactory is responsible for tokenizing the formula in R1C1 format (previously there was a "inline" tokenizer).
But the factory does not recognize R1C1 as a valid InternalAddress so everything else falls off track - lines 154-155 on the TokenFactory.cs.

A duck-tape way to make it work is:
In the ExcelAddress.cs function IsValid (starting at line 882) change line 910 condition - checking if a string is an R1C1 addresses as well. Something like:

if (
IsAddress(intAddress)
|| IsAddress(ToAbs(intAddress, 1, 1, -1, -1)) //Duck-Tape - Check if is in R1C1 format
)

For this to work we have to change the function ToAbs to protected (but I think this is the least of the problems)