Previously i had matched ore density to moreores, but this density was
too high and out of balance with MTGame, reduce density to be similar
to copper ore.
The 2 levels of underground ore were overlapping, fix.
Textures are actually by kilbith, update credits.
Also credit kilbith for bronze, copper, gold and steel blocks, credits
had not been updated at the time.
Some nodes with the snappy group (wool, glass pane, seeds) were missing
sound when dug with a sword.
Adding the sound causes it to be used for glass pane, so define a 'dig'
sound in the 'node sound glass defaults' table, use the footstep sound.
Adding the sound also causes it to be used for seeds which deliberately
have no dig sound, so add an empty sound override for seed dig.
Reduce the gain of the glass footstep sound which was excessively loud.
Add some freesound members to license.txt.
