Tune cave noise scales to 6. Fix blobs spflag, now usable. Update conf.example

6 now seems the best match to me from flying underground and attempting to match caves width visually to my build with the original noise code. Calinou helped me tune the cave width with his experience of the original mgv5, the caves were still too narrow with the noise scale of 7.5.
Kwolekr spotted my mistake with spflags, dirt/sand/gravel/lava blobs are now optional, enabled by default.