Fix issues with copying worksheets across workbooks (#839) ...

* Tests for copying worksheets added

* Add tests for pictures and data validation rules

* Fix test for styles copying

* Extract copying logic into dedicated classes (XLPicture, XLTable, XLNamedRange). Implement copying of conditional formats.

* Implement failing scenario for existing test

* Fixed copying conditional formats

* Fixed copying of merged ranges

* Tests simplified as saving issues must be addressed separately

* Fixed saving the row heights on copied worksheets

* Add tests for copying tables and selected ranges. Fix copying selected ranges.

* Fix copying page setup

* Removed debugging code

* CopyTo and WithoutWorksheet method removed from public API. A new constructor for XLConditionalFormat added. Formatting issues fixed.

* Copying table with or without data implemented. Tests added.

* Revert removing public methods

* Copying pictures within a worksheet implemented. Tests added.

* Tests for named ranges copying added.

* Implement XLPicture.Duplicate method.

* Update doctext

* Fix IXLPicture.CopyTo signature

Use inline out parameters provided by C# 7.2

Add IXLCell.MergedRange()

Escape quotes in worksheet names

Move test to XLWorksheetTests.cs

Case insensitive IXLWorksheets.TryGetWorksheet

Set sheet state to null if it's visible.

Allow rename of sheet by changing case

Check for sheet name before adding. Fixes #378

Unknown changes - something to do with line endings?

Parse commas in print area (#263) ...

* add method to format the defined names if a comma exists in the sheet name

* add Excel workbook to test loading of sheets with commas in them (when they have a print area)

* Regex change to make sure all tests pass successfully

* use String.Format instead of new fangled string interpolation.

* Improve defined name parsing.

* Add unit test for references to a sheet with commas in the name

* Add unit tests and adjust CalcEngine to allow enclosing characters around identifiers

* Reformat code using CodeMaid

* Don't use C#6 syntax for dictionary initialiser.

Project hierarchy cleanup