Make the colours in the demo a bit more logical.

Make the colours in the demo a bit more logical.

Make the colours of the items in the "attributes" column blue/green/red in
order instead of making all odd items blue and all even and divisible by 3
ones green while making the rest of them red -- it was a bit difficult to
figure out how it worked before.

Also correct wxDataViewItemAttr::SetItalic() check: comparing the remainder of
the division by 2 with 5 didn't risk to work.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62385 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775