Don't save empty cells to file, even if they have conditional formatting applied

Update test files. All .xml files now start with 1, i.e. no more sheet.xml (without digit). Digits now also decimal based, not hexadecimal.

Add test for minimum/maximum conditional formatting. Fix test for LowMidHigh (don't output values)

Merge branch 'hotfix' of https://github.com/msntts/ClosedXML into msntts-conditional-format-fix ...

# Conflicts:
#	ClosedXML_Tests/ClosedXML_Tests.csproj

Add unit test for 5bce863

Fix XLColor equals method (#25) ...

* Use ToArgb() to compare equality of colors, in order to return TRUE when comparing RGB(FF,FF,FF) to White.
http://stackoverflow.com/questions/8146453/system-drawing-color-equality-operator-doesnt-treat-0xffffffff-as-color-white

* Add test for named color vs RGB

* Update bespoke unit tests files to remove duplicate font styles.

* Set substringo of rich text to Garamond font, instead of Broadway. Broadway probably isn't installed on the AppVeyor server. Garamond is a much more common pre-installed font.

* Disable different font to see if it affects the AppVeyor build.

* Use Courier font for rich text. Hopefully this one is installed on AppVeyor.

Project hierarchy cleanup