Replace RJ45 jack by Würth 7499010121A

This one appears to be readily available at various distributors.

Also add 3D print models for case parts, obtained from

https://www.eevblog.com/forum/projects/diy-dsoxlan-interface-for-keysight-oscilloscopes/msg4323214/#msg4323214

apparently authored by Jay_Diddy_B.

Adapted layout to fit these models.

dsoxlan.kicad_pro

@@ -34,9 +34,9 @@
         "other_text_thickness": 0.15,
         "other_text_upright": false,
         "pads": {
-          "drill": 3.0,
-          "height": 2.999743,
-          "width": 2.999743
+          "drill": 3.2,
+          "height": 3.2,
+          "width": 3.2
         },
         "silk_line_width": 0.12,
         "silk_text_italic": false,
@@ -911,7 +911,7 @@
       "idf": "",
       "netlist": "",
       "specctra_dsn": "",
-      "step": "",
+      "step": "dsoxlan.step",
       "vrml": ""
     },
     "page_layout_descr_file": ""