Adding Kain sprite and credit for Sithjester

Missed the addition of this spritesheet in a totally unrelated commit a
year ago, and just found this image in the repo with no credit attached.

Renamed the file appropriately and added proper credit to Sithjester.
Next commit will introduce slight character changes to actually make
use of this sprite for the main character.
Added new Player Character sprite

Removed a hack in which the player character loads and uses the npc1
spritesheet, since now the proper script/character-based mechanisms are
in place for setting the player sprite.

Actors are now "spriteless" on initialization, and so some guards were
added to prevent drawing or altering an uninitialized Sprite.

Resized the "kain" spritesheet by 1.5x to match the tile size and other
NPCs. Created an EDS file for the spritesheet. Also altered the "kain"
character archetype to use the new spritesheet.

Removed the map script's code to show the character; in the case of an
intro sequence this should be the responsibility of the chapter script.

Removed some unnecessary debug messages that were accidentally left in
with the last few commits.