begin moving turtle specific code from opus into turtle package

turtle/autorun/startup.lua

@@ -0,0 +1,31 @@
+local Util = require('util')
+
+local device = _G.device
+local fs     = _G.fs
+local turtle = _G.turtle
+
+if turtle then
+  fs.mount('sys/apps/system/turtle.lua', 'linkfs', 'packages/turtle/system/turtle.lua')
+
+  function turtle.scan(blocks)
+    local pt = turtle.point
+    local scanner = device['plethora:scanner'] or error('Scanner not equipped')
+
+    if not blocks then
+      return Util.each(scanner:scan(), function(b)
+        b.x = pt.x + b.x
+        b.y = pt.y + b.y
+        b.z = pt.z + b.z
+      end)
+    end
+
+    return Util.filter(scanner:scan(), function(b)
+      if blocks[b.name] then
+        b.x = pt.x + b.x
+        b.y = pt.y + b.y
+        b.z = pt.z + b.z
+        return true
+      end
+    end)
+  end
+end