Rename to Rack19HalfWidth to better fit with other Rack boxes

Move to Box group
Support more than one row of equipement
Move defaults to arguments to conform with general coding style

boxes/generators/rack19halfwidth.py

@@ -3,32 +3,25 @@
 from boxes import Boxes
 from boxes.edges import Edge
 
-class H19Rack(Boxes):
-    """Half 19inch rack unit for musical equipment."""
-    ru_count = 1
-    holes = "xxmpwx"
-    z = 20
-    deepz = 124
-    earside = 'r'
+class Rack19HalfWidth(Boxes):
+    """Half width 19inch rack unit for musical equipment."""
 
-    # provided by default via boxes
-    x, y, = 0, 0
-    thickness = 3
+    ui_group = "Box"
 
     def __init__(self):
         super().__init__()
         self.argparser.add_argument(
-            '--ru_count', action='store', type=float, default=self.ru_count,
+            '--ru_count', action='store', type=float, default=1,
             help='number of rack units')
         self.argparser.add_argument(
-            '--holes', action='store', type=str, default=self.holes,
-            help='holes, x=xlr, m=midi, p=9v-power, w=6.5mm-wire')
+            '--holes', action='store', type=str, default="xxmpwx",
+            help='mounting patterns: x=xlr, m=midi, p=9v-power, w=6.5mm-wire, space=next row')
         self.argparser.add_argument(
-            '--z', action='store', type=float, default=self.z,
+            '--z', action='store', type=float, default=20,
             help='depth of the shorter (rackear) side')
         self.argparser.add_argument(
-            '--deepz', action="store", type=float, default=self.deepz,
-            help='depath of the longer (screwed to another half sized thing) side')
+            '--deepz', action="store", type=float, default=124,
+            help='depth of the longer (screwed to another half sized thing) side')
 
     def render(self):
         """Render box."""
@@ -59,9 +52,12 @@ class H19Rack(Boxes):
 
     def util_holes(self):
         """Add holes."""
-        self.moveTo(10, self.y / 2 + self.thickness)
-        for hole in self.holes:
+        self.moveTo(10, (44.45 - 4.45)/2)
+        for line in self.holes.split():
+            with self.saved_context():
+                for hole in line:
                     self.hole_map.get(hole, lambda _: None)(self)
+            self.moveTo(0, 44.45)
 
     def hole_xlr(self):
         """Hole for a xlr port."""