[Flare Plugin] Fix coordinate format for import and export

Flare expects object coordinates to be in tiles instead of pixels.
Conversions have been added for Orthogonal and Isometric maps (the
2 that Flare supports).

The export function now writes the orientation of the map. This isn't
used by the Flare engine itself, but it is used when importing Flare
maps into Tiled.
Please use `orientationToString` from `map.h`.