I2C bus reset with status info to user, re issue 1025

[dave-prosee]

I2C slave might stil have something to send when ESP826 starts I2C, thus
keeping the bus stuck.
Happens e.g. when power failure/reset during transmission.
Thanks to work of drmpf there is a solution.
Implemented as separate method (Wire.status()) so as not to interfere with existing.
Method (status)returns one of the five statuses. 0 or I2C_OK is ok.
Other status codes are for hanging SCL or hanging SDA

Usage:

Wire.begin();                                 //like normal
if (Wire.status() != I2C_OK) 
   Serial.writeln(error_msg);                 //Something wrong with I2C bus 
                                              //that cannot be recovered. 
                                              //Perform power cycle 
                                              //or search for other masters on bus;