Add support for CopySheet to HSSFSheet.cs
Allows Color Palettes, styles, and images to be copied along with the sheet
- Fix a bug with CopySheet() that I fixed in CopyTo() that causes corrupt cell text.
- Updated comment for a method to properly reflect its current purpose.
Added example project showing how to copy sheets between documents.
Added unit tests for Sheet copy methods
Merge branch 'master' of https://github.com/Sappharad/npoi into Sappharad-master
use NUnit instead of MSTest as the unit test framework for TestCopySheet.cs

Remove solution\visualstudio\NPOI.Examples.sln. It should be in Examples
folder