Refactor type generator

* Allows for generating top-level types for any embedded struct so
  that sub-types can be properly instantiated from calling code
  * Specifying `-no-embedded-types` will generate top-level types
    rather than embedding the struct

* Refactored "Device" API
  * All fields set to `omitempty` because it describes all possible
    device types, so effectively any field could be omitted any time
  * Fixed `get` call for "Device" API; replacing `rest` with `stat`

* Generated `get` and `update` calls for `Setting*` APIs

* Added `5.14.23` JSON files

fields/5.14.23/SettingSnmp.json

@@ -0,0 +1,7 @@
+{
+  "enabled": "true|false",
+  "enabledV3": "true|false",
+  "community": ".{1,256}",
+  "username": "[a-zA-Z0-9_-]{1,30}",
+  "x_password": "[^'\"]{8,32}"
+}