Breaking changes

Range strings, e.g. A1:B2 are now always treated as absolute, i.e. relative to A1 instead of relative to the top left cell of a given range.
IXLSheetProtection has been totally refactored and now uses a flag based enum to control the elements that are allowed or locked.
Removed IXLSheetProtection.IsProtected setter
XLClearOptions and XLCellUsedOptions 's flags are now aligned

Enhancements

#1015 Text join func enhancement (Thanks @James-Whitfield)
#1038 IXLSheetProtection refactoring
#1054 Implement workbook FileSharing and a few of the properties
#1058 Dont recalculate formula cached values after load
#1077 Refactor digit and letter parsing to allow Unicode characters
#1109 Don't automatically adjust columns width to contents when inserting datatable. Some users want to opt out because of PlatformNotSupportedException
#1129 Implementation pivot table formats (Thanks @b0bi79)
#1130 Enhance TRUNC function for additional parameter
#1136 Implement NUMBERVALUE function
#1151 Performance improvement to delete entire columns
#1158 Check that print titles are valid row ranges or column ranges
#1170 Remove IXLSheetProtection.IsProtected public setter

#1063 Copy comment style correctly when shifting ranges
#1108 Correctly save empty cell with quote prefix (do not treat as empty)
#1132 <c> elements with missing r attribute: XLAddress constructor had parameters swapped
#1133 Enumerate ranges in a deterministic order
#1134 Correctly propagate worksheet style to cells from a worksheet
#1135 Correctly load column-wide styles
#1137 Fix changing inner borders of the range
#1150 Correctly clear inline string when required
#1153 Correctly throw DivisionByZeroException when denominator is zero.
#1155 Ignore _X (capital X) as XML escaping char
#1161 Avoid creation of new item in Internals.RowsCollection when adding comment
#1168 Fix initialization of default styles for XLCells, XLRows, XLColumns and XLRanges

Thanks to @Pankraty for many PRs, as usual.