Machine casing item

The casing is intended to be an ingredient in craft recipes for machines.
It isn't actually used in any recipes yet.  Although mainly a craft
item, it is defined as a node type, mainly to get an appropriately cubic
inventory image.  It is incidentally possible to place it as a node:
this makes some sense, although the empty machine casing isn't actually
useful as a node.
Use machine casing in most machine recipes
Consistently use cable in electric machine recipes

All electric machine recipes now include cable of the appropriate tier
as the bottom-middle ingredient, immediately below the casing ingredient.
Many LV machines were using a copper ingot in that location.
Tweak supply converter recipe

The casing is now in the center of the grid, as it is for all other
machines.
Fine gold and silver wire items

Not used in any recipes yet.
Remove duplicate cable textures

Some of the technicx32 cable textures were just duplicates of the
standard-resolution textures.
Vary cable insulation type with tier

LV cables are now paper-insulated, rather than uninsulated (which made
no sense).  MV cables are rubber-insulated as before.  HV cables are now
plastic-insulated (which they already visually appeared to be).  MV and
HV cables are still crafted by adding insulation onto lower-tier cable,
rather than by insulating raw copper; this matches the way machines are
upgraded between tiers rather than crafted afresh.
Exclude technic:nothing from creative inventory
Rework some recipes to use more varied ingredients
Tweak energy crystal recipes

Use silver instead of gold in the recipe for the red energy crystal,
and mithril instead of gold in the recipe for the blue energy crystal.
This provides more appreciable steps in the expense of the upgrades,
which were too similar, and in particular makes the blue energy crystal
less ridiculously cheap.