By Duncan Miriri and Karin Strohecker NAIROBI (Reuters) – Millions of Kenyans will head to the polls on Tuesday to pick a new president in a fiercely contested election that pitches veteran opposition leader Raila Odinga against Deputy President William Ruto. President Uhuru Kenyatta is not running due to term limits but is backing Odinga. Lawmakers and country officials will also be elected. The final four opinion polls published last week put Odinga ahead with a margin of 6-8 points but Ruto has dismissed them as fake and designed to sway the electorate. Following are key topics for investor…