Add support for sending missing context field on main messagebus

[AIIX]

Context fields were previously ignored from being sent as they weren't previously useful but have always been part of the messagebus message format

• Hivemind makes use of the context message to route incoming messages to Mycroft core in the mesh network by adding source and destination fields
• This PR adds the sending of context messages only if hivemind protocol is enabled in the Global Settings as too safeguard all other implementations using the sendRequest and sendBinary functions from Mycroft Connect
• Context messages are by default set to as empty when not used
• Only sendText function utilized by the text field in the Mycroft GUI application sends the context fields in the message currently