Various inputs around Layer Management should allow negative numbers

[OtherworldBob]

Various inputs in Maniac around Layer Management are currently locked to only allow positive numbers.
This is due to the data types currently being used in the RSDKv5 project.

I believe at a minimum, UnknownWord (aka UnknownValue) 1 & 2, as part of the SceneLayer and ScrollInfo objects should be changed to Signed short values, and thus allow negative numbers. This should then filter up into Maniac itself.

In my testing, setting this values near the maximum for an unsigned short reverses their effects in-game: i.e. the layer starts scrolling in the opposite direction, compared to a value near 0.

[OtherworldBob]

#13 Has been merged.
I haven't gone as far as renaming the internal RSDKv5 values yet, as I suppose there may be more knowledge to be mined yet. But I think everything else is still playing nicely.