Allowed special characters in structured references

Characters <>:"/\|?* were not allowed in the column specifiers of
structured references. This removes this limitation and adds test.
Fixes #34

Author: Efthimia Aivaloglou

src/XLParser.Tests/data/testformulas/structured_references.txt

@@ -25,4 +25,5 @@
 =DeptSalesFYSummary['#OfItems]
 =DeptSales[ [SalesPers]:[Region] ]
 =DeptSales[[#Headers], [#Data], [ComPct]]
-=DeptSales[@Column]
+=DeptSales[@Column]
+=Tabel25[[#This Row],[I/HV]]

src/XLParser/ExcelFormulaGrammar.cs

@@ -150,7 +150,7 @@ public class ExcelFormulaGrammar : Grammar
         { Priority = TerminalPriority.FileNameNumericToken };
 
         private const string fileNameForbiddenCharacter = @"<>:""/\|?*";
-        private const string fileNameRegex = @"\[[^" + fileNameForbiddenCharacter + @"\[\]]+\]";
+        private const string fileNameRegex = @"\[[^\[\]]+\]";
         public Terminal EnclosedInBracketsToken { get; } = new RegexBasedTerminal(GrammarNames.TokenEnclosedInBrackets, fileNameRegex)
         { Priority = TerminalPriority.FileName };