Fix door's glitch in creative mode

For better crafting and modding.

also, license follows the default one since thats how the textures for
minetest_game usually work.

Fixed default_grass_side.png

object found *among* the stone.

That is, mese should behave such that you get something potentially useful out
of the aggregate block you just broke, rather than just collecting the whole
block when mined.

Mese crystals in stone give a single Mese Crystal when mines. Craft three of
those + 2 sticks for Mese Pickaxe, or 9 for a Mese block. Craft one Mese
Crystal by itself to get 9 Mese Crystal fragments, which all mods should use
when a full Mese Crystal is too much.

This includes new textures for the above objects, tweaks to the sounds used for
them, and naming tweaks for the textures used for default mese in stone, so
that old texture packs don't use the "wrong" image.

This represents my best effort to match C55's suggestions.

Fix incorrect slabs to full block transformation by changing the modname to 'stairs' for all stairs and slabs

Fix the death animation looping while the player is dead, by using a still frame instead (I don't believe the amount of detail for a full animation is needed anyway). Also call the animation Lay instead of Death, so other mods like beds can use it

VanessaE suggested a sit animation, so add one to the player. Not used by default, but many mods might find this handy