Superficially fix basic mcl support

[corarona]

This fixes a few issues that kept the mod from running in mcl (there are probably more but with this it doesn't crash on load or spawning dragon or quickly after...):

Fixes #34
Fixes #32
Fixes #33
Fixes #36
Fixes #35

• Fix instances where minetest.is_creative_enabled is wrongly called with the object
• Fix a too early access of the "steel_ingot" variable in nodes.lua which is only ultimately set on_mods_loaded when using mcl (or another game that doesn't have an item name containing "steel_ingot" but one containing "iron_ingot" to be precise)
• Added draconis.global_nodes for mcl*
• Added node sound functions for mcl* in global table
• Added a default value to all occurences of self.turn_rate in behaviors.lua (no idea if this is the way to go, but it appears to fix Crash on "field turn-rate is nil" #33 and crash on spawn dragon 2 in MineClone/MineClonia #36

Cherry pick at the individual commits if you don't like all of them ... but at least the first 4 are undeniably correct imo ^^

More work needed

This fixes the mod to the point that draconis loads without crashes in mcl and dragons can be spawned and fight each other without crashing the game.

Probably still problematic:

• As far as I have seen no "dragon nests" spawn in mcl probably because of the different node names haven't really looked into it yet. Dragon nests spawn on tree tops and probably other "weird" locations!?
• Dragons can not be damaged by mcl players and other mcl damage events (? - see https://git.minetest.land/MineClone2/MineClone2/pulls/3433 )
• I have also not tested any other deeper gameplay aspects, the special "dragon tool" stuff would need adjustment for mcl as well as any custom nodes in the mod and likely some other stuff.

[corarona]

As far as I have seen no "dragon nests" spawn in mcl probably because of the different node names haven't really looked into it yet

ok looks like i was wrong about that one, could use some adjustment though ^^