software/kvm: add 1-machine & frontend schema

software/kvm/instance-kvm-frontend-schema.json

+{
+  "properties": {
+    "frontend-instance-guid": {
+      "title": "Frontend Instance ID",
+      "description": "Unique identifier of the frontend instance, like \"SOFTINST-11031\".",
+      "type": "string"
+    },
+    "frontend-software-type": {
+      "title": "Frontend Software Type",
+      "description": "Type of the frontend instance, like \"RootSoftwareInstance\".",
+      "type": "string",
+      "default": "RootSoftwareInstance"
+    },
+    "frontend-software-url": {
+      "title": "Frontend Software URL",
+      "description": "Software Release URL of the frontend instance, like \"http://example.com/path/to/software.cfg\".",
+      "type": "string",
+      "format": "uri",
+      "default": "http://git.erp5.org/gitweb/slapos.git/blob_plain/HEAD:/software/apache-frontend/software.cfg"
+    },
+    "frontend-additional-instance-guid": {
+      "title": "Additional Frontend Instance ID",
+      "description": "Unique identifier of the additional frontend instance, like \"SOFTINST-11031\", if empty won't be requested.",
+      "type": "string"
+    },
+    "frontend-additional-software-type": {
+      "title": "Additional Frontend Software Type",
+      "description": "Type of the frontend instance, like \"RootSoftwareInstance\".",
+      "type": "string",
+      "default": "RootSoftwareInstance"
+    },
+    "frontend-additional-software-url": {
+      "title": "Additional Frontend Software URL",
+      "description": "Software Release URL of the frontend instance, like \"http://example.com/path/to/software.cfg\".",
+      "type": "string",
+      "format": "uri",
+      "default": "http://git.erp5.org/gitweb/slapos.git/blob_plain/HEAD:/software/apache-frontend/software.cfg"
+    }
+  }
+}