Heating oil prices in Maine are heading back up.  The Governor's Office of Energy Independence and Security says the statewide average cash price for No. 2 heating oil has risen 10 cent a gallon since last week to $2.38.  The increase reflects a rise in wholesale energy prices, a result of concern over instability in the Middle East and the dispute over natural gas supplies between Ukraine and Russia, says OEIS director John Kerry.  Kerry says heating oil prices in Maine range from a low of $2.06 in southwestern Maine to a high of $2.60 in eastern Maine.  Kerosene in Maine is selling for an average price of $2.86 a gallon.