Check if generated map file is within size range

[boldtrn]

As mentioned by Ludwig here:
The size check before overwriting was also useful.

The idea is to check the size of the newly generated map compared to the old map. If the new file is smaller by e.g. 10% we would thrown an error.

[devemux86]

Bash can probably provide such functionality.

[devemux86]

Creator builds maps without automatically overwriting old ones.
Then checks if new size < 70% old size to reject or keep them.