Module loading upgrade

This all started because I wanted the UnixCompleters module and
initialization to move to the base.linux package.

* MyConfig.class modified to load from all modules
* Test-MyModules suppress empty entries
* removed unix entries from base/src/modules.json
+ created base.linux/src/modules.json

base/src/modules.json

@@ -4,11 +4,4 @@
     "oh-my-posh",
     "posh-git",
     "z"
-  ],
-  "Desktop": [
-  ],
-  "Unix": [
-    "Microsoft.PowerShell.UnixCompleters"
-  ]
-  
-}
+  ]}