Allow 1-tile spell AoE

[Venera3]

Summary

None

Purpose of change

Allow spells to define one-tile AoEs (currently e.g. a blast is either 1x1 only affecting the target tile or ~5x5).

Describe the solution

AoEs below 1 will default to only painting the target tile.

Describe alternatives you've considered

None

Testing

Preceding the changes defined a blast spell with an AoE of 1, only the target tile is affected. Redefined the AoE as 2, a 5x5 circle is hit.
After the changes an AoE of 1 hits a 3x3 area, other sizes are not affected.

Additional context