Fix null exception when removing pivot cache. Thanks to https://github.com/jafin for pointing it out.

Delete orphaned pivot caches when deleting a worksheet. Actually we need Worksheet.PivotTables to be populated on file load, but that will be done later.

When saving, don't create a cell object if it's not going to be used.

Add null check for cell.InlineString.Text

Cache ToInvariantString

IsMerge is now faster.

Merge branch 'PerformanceImprovementsCombined' of https://git01.codeplex.com/forks/albinsunnanbo/closedxml into AlbinSunnanbo/closedxml

Improve performance of GetColumnLetterFromNumber by using a lookup of letters instead of modulo/reminder counting for low numbers ...

Gives overall speed improvement of CreatePackage by 4%

Performance improvement, creating thread static instances of Bitmap and Graphics objects to ...

enable maximum reuse while still being thread safe

Saves ~30% performance on AdjustToContents

Add PerformanceRunner

Heights and widths no round to 6 decimal places.

Use bin folder for test output.

Merge branch 'AlbinSunnanbo/closedxml'

Merge branch 'GitIgnorePackages' of https://git01.codeplex.com/forks/albinsunnanbo/closedxml into AlbinSunnanbo/closedxml

Merge branch 'AlbinSunnanbo/closedxml'

Merge branch 'DisposeFontFromFontCache' of https://git01.codeplex.com/forks/albinsunnanbo/closedxml into AlbinSunnanbo/closedxml

Merge branch 'AlbinSunnanbo/closedxml'

Merge branch 'FixTestsForSwedishCulture' of https://git01.codeplex.com/forks/albinsunnanbo/closedxml into AlbinSunnanbo/closedxml

Don't include empty cells

Fix time zone issue in tests

Updated example files, set applyNumberFormat=1 and applyAlignment=1 ...

Made example data match updated code in
previous commit:
> Hash: 015fdc8
> Message: Set ApplyNumberFormat and ApplyAlignment to true

To make sure only the specified fileds were updated I made a small program (source code below) to manipulate existing files
---------------------------------------------------
using System;
using System.IO;
using System.IO.Compression;
using System.Linq;

namespace ZipMod
{
    class Program
    {
        static void Main(string[] args)
        {
            Directory.SetCurrentDirectory(@"C:\Git\closedxml\ClosedXML\ClosedXML\ClosedXML_Tests\Resource");
            foreach (var excelFile in Directory.EnumerateFiles(".", "*.xlsx", SearchOption.AllDirectories)
                .Where(f => !f.Contains("svnbridge"))) // Skip svnbridge files since some are corrupt
            {
                Console.WriteLine(excelFile);
                using (FileStream zipToOpen = new FileStream(excelFile, FileMode.Open))
                {
                    using (ZipArchive archive = new ZipArchive(zipToOpen, ZipArchiveMode.Update))
                    {
                        ZipArchiveEntry stylesEntry = archive.GetEntry("xl/styles.xml");
                        string content;
                        using (StreamReader reader = new StreamReader(stylesEntry.Open()))
                        {
                            content = reader.ReadToEnd();
                        }
                        content = content.Replace("applyNumberFormat=\"0\"", "applyNumberFormat=\"1\"").Replace("applyAlignment=\"0\"", "applyAlignment=\"1\"");
                        using (StreamWriter writer = new StreamWriter(stylesEntry.Open()))
                        {
                            writer.BaseStream.Seek(0, SeekOrigin.Begin);
                            writer.BaseStream.SetLength(0); // Clear
                            writer.Write(content);
                        }
                    }
                }
            }

            Console.WriteLine("Done");
            Console.ReadKey();
        }
    }
}
---------------------------------------------------
Sorry for the excessive commit message

Compare two streams using strings to overcome some issues where stream lengths differed while the content was equal

Add NuGet packages folder to .gitignore for convenience

Properly dispose the fonts in the fontCache

Set culture to en-US to pass the tests DataTypes, Dollar and Fixed on a computer with the sv-SE locale ...

note: sv-SE has "," as decimal separator, " " as thousands separator and put CurrencySymbol after the digits, not before.

Add Remove and RemoveAll methods for conditional formats.

Fix issue when changing a table column names

Set ApplyNumberFormat and ApplyAlignment to true

fixed comments formatting error

Added IsBlank