Implements feature for animations to spawn additional animations.

[CCHyper]

Closes #752, Closes #883

This pull request implements a new system for AnimTypes, allowing them to spawn additional animations at the start, middle and end of their sequence stages. All animations spawned will be from the center coordinate of the animation spawning these additional animations.

NOTE: The <stage> keyword used below can be replaced with; Start, Middle, End.

[AnimType] <stage>Anims=<comma delimited list of AnimTypes> List of animations to spawn at the designated stage of the animation sequence. Defaults to <none>.

<stage>AnimsMinimum=<comma delimited list of integers> The minimum number of animations that can spawn when choosing the random amount for each of the respective entries on the animations list. This list must have the same number of entries as the animations list. Defaults to 1 for each entry.

<stage>AnimsMaximum=<comma delimited list of integers> The maximum number of animations that can spawn when choosing the random amount for each of the respective entries on the animations list. This list must have the same number of entries as the animations list. Defaults to 1 for each entry.

<stage>AnimsCount=<comma delimited list of integers> Number of animations to spawn for each of the respective entries on the animations list. This list must have the same number of entries as the animations list. Defaults to 1 for each entry, and takes priority over the Minimum and Maximum entries.

In addition to this new system, a new key for setting the logical middle frame (the frame in which the craters etc, are spawned) can now be set.

MiddleFrame=<integer> The frame number in which the animation system will spawn various logics (e.g. craters, scorch marks, fires). Defaults to auto-detect based on the largest frame of the shape file. A special value of -1 can be used to tell the animation system to use the exact middle frame of the shape file (shape file has 30 frames, frame 15 will be used).