MapService Refactor Part 2

Refactors the following:

Move otiIndicatorsMapService.modes to
OTIMapService._availableTransitModes

Move getLegendData to MapService, and fires
AvailableModesUpdated event

Moves getMapInfo to getMapExtent and rejects promise
if no map extent data

Refactors all initialization logic in root-controller to
the initialize function, and moves the init function off
the $scope