Allow Setting Default transcription state

When creating a new extension/voicemail box it can have a global/domain default setting for whether to enable transcription.
`transcription_enabled_default` default setting that determines what status transcription should be for all new extensions/voicemails.

app/extensions/extension_edit.php

@@ -559,6 +559,7 @@
 											$array["voicemails"][$i]["voicemail_enabled"] = $voicemail_enabled;
 											$array["voicemails"][$i]["voicemail_description"] = $description;
 											$array["voicemails"][$i]["voicemail_tutorial"] = $voicemail_tutorial;
+											$array["voicemails"][$i]["voicemail_transcription_enabled"] = $_SESSION['voicemail']['transcription_enabled_default']['boolean'] ?: false;
 									}
 							}