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/Chart.yaml

@@ -5,5 +5,5 @@ icon: https://avatars.githubusercontent.com/u/136759148
 
 type: application
 
-version: 3.1.2+up6.0.0.beta12.1
+version: 4.0.0+up6.0.0.beta12.1
 appVersion: "6.0.0-beta12.1"