add support of row's color and backgroundcolor

[SuperGod]

add two function,so user can controll each row's color and background color

[lxn]

Thanks for doing this, but I would like you to make some improvements:

• Instead of the proposed TableRow struct and the two new color setter methods, use an approach like ImageProvider, maybe call it ColorProvider.
• This ColorProvider interface would have to be handled in reflectmodels.go, as well.
• Also please add yourself to the AUTHORS file.

Now I regret adding the AlternatingRowBGColor stuff, when it should have been done with a ColorProvider interface.