Improve MQTT handling and use cache for incorrect battery and charge remaining readings

[altserg]

1. Bypass cache when sending MQTT messages This fixes the problem of sensor data unavailable after HASS or MQTT broker restart
2. Send persistent HASS discovery messages, report discovery message send errors
3. Send cached values of battery level and charge remaining in case the reading from vehicle are incorrect

[buxtronix]

This will need to be fixed to work with the new viper flag methods.

[altserg]

Resolved conflicts

[buxtronix]

thanks again for the change!

[altserg]

For some reason, some of my changes were not integrated. I will submit couple of more patches