TeamSpeak chart: naming scheme, hardening, configurable node ports

Batch-3 major PR for teamspeak-server (issue #32):

- Rename service and StatefulSet to the repo naming scheme
  ({{ .Release.Name }}-{{ .Chart.Name }}-service / -sfs); the PVC keeps
  its historical name (documented naming exception, data preservation).
- NodePorts configurable via server.voicePort / server.fileTransferPort
  (defaults 30987/30033, satisfactory pattern); ports are also passed to
  the server via TSSERVER_DEFAULT_PORT / TSSERVER_FILE_TRANSFER_PORT.
- Hardened, values-configurable security contexts
  (securityContext.pod/container): non-root uid/gid 9987,
  readOnlyRootFilesystem, all capabilities dropped.
- Probes values-configurable (defaults unchanged).
- Additive env value rendered through tpl (value/secretKeyRef/
  configMapKeyRef forms).
- Chart 3.1.2 -> 4.0.0 (+up6.0.0.beta12.1).

teamspeak-server/templates/teamspeak-server.service.yaml

@@ -1,19 +1,21 @@
 apiVersion: v1
 kind: Service
 metadata:
-  name: {{ .Release.Name }}-service
+  name: {{ .Release.Name }}-{{ .Chart.Name }}-service
+  labels:
+    app: {{ .Release.Name }}-{{ .Chart.Name }}-service
 spec:
   selector:
-    app: {{ .Release.Name }}-server-sfs
+    app: {{ .Release.Name }}-{{ .Chart.Name }}-sfs
   ports:
-    - port: 30987
+    - port: {{ .Values.server.voicePort }}
       name: voice-port
       targetPort: voice-port
       protocol: UDP
-      nodePort: 30987
-    - port: 30033
+      nodePort: {{ .Values.server.voicePort }}
+    - port: {{ .Values.server.fileTransferPort }}
       name: file-transfer
       targetPort: file-transfer
       protocol: TCP
-      nodePort: 30033
+      nodePort: {{ .Values.server.fileTransferPort }}
   type: NodePort