Finish Omnicoins -> Nomicoins change

Rename textures from Omnicoin -> Nomicoin

This prevents resource packs from overriding these textures with an 'omnicoin' one.

Item IDs have not been changed, for backwards compatibility.

This is the rest of the changes from f94dd1233b.

overrides/resources/contenttweaker/models/item/omnicoin.json

@@ -1,6 +1,6 @@
 {
   "parent": "item/generated",
   "textures": {
-    "layer0": "contenttweaker:items/omnicoin"
+    "layer0": "contenttweaker:items/nomicoin"
   }
 }

overrides/resources/contenttweaker/models/item/omnicoin100.json

@@ -1,6 +1,6 @@
 {
   "parent": "item/generated",
   "textures": {
-    "layer0": "contenttweaker:items/omnicoin100"
+    "layer0": "contenttweaker:items/nomicoin100"
   }
 }

overrides/resources/contenttweaker/models/item/omnicoin25.json

@@ -1,6 +1,6 @@
 {
   "parent": "item/generated",
   "textures": {
-    "layer0": "contenttweaker:items/omnicoin25"
+    "layer0": "contenttweaker:items/nomicoin25"
   }
 }

overrides/resources/contenttweaker/models/item/omnicoin5.json

@@ -1,6 +1,6 @@
 {
   "parent": "item/generated",
   "textures": {
-    "layer0": "contenttweaker:items/omnicoin5"
+    "layer0": "contenttweaker:items/nomicoin5"
   }
 }