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

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

Fix saving alignment

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Do not quote worksheet name with whitespace when saving pivot table worksheet source

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

Add to IXLTableField: HeaderCell, TotalsCell and DataCells

Fix pivot table integrity when saving multiple times.

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

Allow Guid values to be inserted

Implement IXLTable methods for appending and replace table data

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

Add tests for column letter lookups

Maintain pivot table page field order

TryGetValue should return false if formula evaluation fails

Implement the full range of Item subclasses for pivot tables ( https://msdn.microsoft.com/en-us/library/documentformat.openxml.spreadsheet.shareditems.aspx )

Add and implement IXLAutoFilter.Reapply()

Clear pivot table rendered range upon loading to avoid conflict on rendered cells when opening the file.

Add helper method VisibleRows for autofilters

Allow pivot tables to have no theme

Correctly determine used range when there are merged ranges on a worksheet (fix #881) (#887) ...

* Failing tests added

* Failing tests for predicates added.

* Missing predicates added to LastCellUsed and FirstCellUsed

* Analyze merged ranges with any value of includeFormats flag.

* Use extension method instead of two comparisons

* Use null propagation for predicate

Correctly unprotect worksheet without password

Ignore pivot table data field base items that are out of range.

Use current locale in test instead of invariant culture as CellValue parsing expects localized values.

Make range address invalid on worksheet deleting. ...

Handle invalid ranges in XLNamedRange.
Re-implement XLAddress and XLRangeAddress ToString* methods to correctly process #REF!

Improve XLCell.SetValue(object) by removing unnecessary TryParse functions ...

Consolidate and improve SetValue(object value) and SetValue<T>(T value)

Bug fix - unsupported CellValues.String Data type ...

Changes at workbooks loading and unit test with file example to test changes.

Pivot table: DateTime type with empty value (Issue #859 fix) (#860) ...

issue #859 : Pivot table: DateTime type with empty value