Splits HAL Digital and Analog Headers into multiple headers (#52)

The Digital and Analog headers (and the implementations, but that will
be moved over later) are just too big and congested. This splits those
headers, and then changes the few things that needed to be changed in
WPILib to get the code working again. No function changes were made in
this commit.

hal/include/HAL/I2C.h

@@ -0,0 +1,14 @@
+#pragma once
+#include <stdint.h>
+
+extern "C" {
+void i2CInitialize(uint8_t port, int32_t* status);
+int32_t i2CTransaction(uint8_t port, uint8_t deviceAddress, uint8_t* dataToSend,
+                       uint8_t sendSize, uint8_t* dataReceived,
+                       uint8_t receiveSize);
+int32_t i2CWrite(uint8_t port, uint8_t deviceAddress, uint8_t* dataToSend,
+                 uint8_t sendSize);
+int32_t i2CRead(uint8_t port, uint8_t deviceAddress, uint8_t* buffer,
+                uint8_t count);
+void i2CClose(uint8_t port);
+}