Improve README.md: ...

Add formula to code example
Remove git screenshot

Update project description in other files

Update release badget version

Updated project description

Merge branch 'release-candidate' into develop ...

# Conflicts:
#	ClosedXML/Excel/XLWorkbook_Load.cs
#	ClosedXML_Tests/Resource/Other/StyleReferenceFiles/TransparentBackgroundFill/TransparentBackgroundFill.xlsx

Fix saving alignment

Fix loading transparent fill

Add ability to set cell value to an enum value

Aggregate color conversion in one place.

Do not quote worksheet name with whitespace when saving pivot table worksheet source

Set IXLCell.Style.IncludeQuotePrefix to true if user sets IXLCell.Value to something that starts with single quote (in line with Excel)

Implement OpenXML's CellFormat.QuotePrefix

Add support for propagating extra columns' formulas and values when replacing / appending data in a table

Fix bug in bounds check. Parameter is based on "first" row or column

Add to IXLTableField: HeaderCell, TotalsCell and DataCells

Improve doctext to indicate relativity of Row() and Rows() parameters

Fix pivot table integrity when saving multiple times.

Throw exception upon saving when table has no data range rows.

Refactor: Move cell value setting to string type into SetKnownTypedValue, but sometimes don't accept strings, e.g. for cell.Value = "2018-06-01";

Allow Guid values to be inserted

Implement IXLTable methods for appending and replace table data

Fix table row offset bug

Reuse custom file properties part instead of creating new one

Store picture markers against a range, rather than an address to benefit from range repository notifications

Exclude full span addresses from range change notifications

Delete table rows correctly

Fix determining the column letter by index

Add tests for column letter lookups

Crop and scale readme.png

Remove obsolete XLAddressLight