Updated nvd3 css and charts to class their svg so its styling won't interfere with other svg libs
[428] Partial fix for 428, Updated line charts guild line mouse over event to use a settable custom formatter for the value field. Otherwise uses the xAxis formatter.  This is only available to line chart and only for value and only is applied to guidelines for now.
updated custom tool tip x formatter to be in src. Also added the remove chart on empty fix for pie only.