* fix compiler warning in SerialPortManager.cpp: function must not
return void
* clean up and simplify implementation of usesHwPort2()
* make const
* overrides are final
* default implementation returns false
* implement in header, as the implementation is very simple
* rename PortManager to SerialPortManager. as "PortManager" is too
generic, the static instance of the serial port manager is renamed to
"SerialPortManager". the class is therefore renamed to
SerialPortManagerClass, which is in line with other (static) classes
withing OpenDTU(-OnBattery).
* implement separate data ages for MPPT charge controllers
* make sure MPPT data and live data time out
* do not use invalid data of MPPT controlers for calculations
* add :key binding to v-for iterating over MPPT instances
this change adds support for a second Victron MPPT charge controller
using a second serial connection.
* Add device configuration for a second victron mppt
* Update VedirectView for second victron mppt
* Update MqttHandleVedirect for second victron mppt
* Update MqttHandleVedirectHass for second victron mppt
* Handle nonexisting victron controllers with optionals
* Add bool-function to Battery and inherited classes, if uart port 2 is
being used
* Introduced a serial port manager. In order to prevent the battery and
the Victron MPPT to use the same hw serial ports, this class keeps
track of the used ports and their owners.
