Change #ship_data.course to float() from integer()
erltrek_galaxy: Add more typespecs
erltrek.hrl: define galacoord() as float()
Add galacoord() conversion offset for erltrek_calc:quadsect_to_galaxy/1

* Adding 0.5 for the x and y coordinates
  is required to mitigate the integer truncation
Fix typo on galacoord() definition