v4.3.0 Improvements and additions

• Added default constructors to all the classes that hadn't. Addition required for some dinamically created objects.
• Added the use of standard GPIO_NUM_NC to define an invalid pin number (non connected)
• Added the use of standard GPIO_NUM_MAX to validate the pin number for verifications
• All pin related constructor parameters types have been changed from uint8_t to int8_t, to make easy use of the GPIO_NUM_NC macro value (-1). All operations are bit equivalent from one to another, as 0xFF was used for own designated invalid pin value, and testing cases used showed no need to change code, but must be carefully tested in any particular case