Monster Bash: Tweak sprite writer
Add support for getting and setting image hotspots and hitmap rectangles

Also include support for getting and setting these values for Monster Bash
sprites.
New test: Overwrite first tile with different data
New test: Resize and overwrite first tile in tileset
Dangerous Dave: Fix tileset format and add test code
Halloween Harry: Don't return default palettes if none specified

This is the job of the image handler to fall back to a default palette.
Add a new filter which is able to add and remove padding bytes

This is used by some graphics formats which have an extra byte every 64kB.
Dangerous Dave: Replace offset tweaking with padding filter

Now an extra byte is inserted every 64kB which fixes problems with the padding
byte being lost after a tile changes size.
Monster Bash: Update sprite handler with Lemm's findings

Now sprites are written out correctly and the game will load them.