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.

Merge branch 'fix-workbookproperties-customdatetimeproperty' of https://github.com/igitur/ClosedXML into igitur-fix-workbookproperties-customdatetimeproperty

Project hierarchy cleanup