RFPlayer : start plugin with no equipment

[jmberhault]

If we start the plugin without the equipment, the plugin state is "starting". It should have the state (or equivalent) : "equipment not found".

[jano42]

Probably fixed by #283

[jano42]

Need an evolution of AsyncSerialPort to have differences between:

• serial port not found (in case of use of an misconfigured plugin, or a serial port name whih have changed)
• serial port open, but no answer from equipments (in case of using physical serial port on computer, but without connected eqipments)

The serial port should manage a machine state like this:

• opening serial port
• serial port opened
• connecting to equipment (may require the caller to provide initiliazation code)
• connected
• closed

[jano42]

Fixed in branch 2_0_0 by https://github.com/Yadoms/yadoms/commit/2a19d8a2a01989a33e70f5481dfa38d629f9b793