Look at both worksheet autofilter as well as table autofilters to determine to leave space for arrow

It's possible to have duplicate default cell styles - occurs when file gets saved under different cultures. ...

We prefer the style that is named 'Normal'

Improve performance of Column.AdjustToContents() for large spreadsheets.

Text() function - return string as is if input value is already a string

Add VmlDrawing Id's to context to avoid reuse.

Don't reference cell to get row height - it will create new unused cell in cells collection.

Clean up unit test.

Add unit test

Overwrite cell number format only if it isn't formatted already.

Better detection of numerical data types. Not only System.Double.

Remove orphaned drawings from worksheets

Preserve whitespace in cells.

Update pivot table reference file.

Merge remote-tracking branch 'upstream/develop' into issue191-classic-pivottable-layout

Classic layout is disabled by default. Fixes #191

Deduce default header and footer font from worksheet, rather than workbook default style

Correctly deduce data type from number format string if data type is number (as for LibreOffice files). ...

Fixes #181

Implement sheet zooming

Cap column width at 255

A data field can be both a label and a value field.

Check for nulls when loading pivot tables

Add pivot table to test for when field is both a label and a value field.

Force OpenXMLValidator to run under invariant culture.

Add unit test to save and VALIDATE file in given non-en-US culture.

Add unit test.

Explicitly ignore custom sheet views and its child elements.(until they are implemented).

Fix some maths and statistical functions. Add statistical functions unit tests.

Merge pull request #154 from b0bi79/develop ...

Shift page breaks

Sort page breaks

Fix test names