I2c reset functionality (#678)

* Addition of a i2cReset method and timeout handling for the case where the i2c hardware FSM (state machine) gets stuck in a busy state.

* Use newly added i2cReset function within the wire library.

libraries/Wire/src/Wire.cpp

@@ -211,4 +211,11 @@ void TwoWire::flush(void)
     txLength = 0;
 }
 
+void TwoWire::reset(void)
+{
+    i2cReset( i2c );
+    i2c = NULL;
+    begin( sda, scl );
+}
+
 TwoWire Wire = TwoWire(0);

libraries/Wire/src/Wire.h

@@ -72,6 +72,8 @@ public:
     int peek(void);
     void flush(void);
 
+    void reset(void);
+
     inline size_t write(const char * s)
     {
         return write((uint8_t*) s, strlen(s));