Add new arg parameter to GenerateTags for configuring output image scale

[nyukhalov]

The following command will make apriltags where the size of 1 bit is 32 pixels.

java -cp april.jar april.tag.GenerateTags april.tag.Tag36h11 ./tags 32

The change is backward compatible, hence running the command without specifying the scale factor will make apriltags where the size of 1 bit is 1 pixel.