Feature/uart logging

This will introduce the logging mechanism to output formatted text on the UART interface (pins P10.4 and P10.5.)
We have a basic and light implementation of sprintf working that can handle the cases in the exemple below.

To test it, one can add the following code in the main function.
He also needs to enable the appropriate "#define" in config.h.

```
// Enable logging and debug interfaces
#ifdef CONFIG_LOGGING
EnableLogging();
#endif

char *s = "test";
char c = 'X';
int i = -12345;
unsigned int u =  12345;
long l = -1234567890;
unsigned long n =  1234567890;
unsigned x = 0xABCD;

Log("String        %s", s);
Log("Char          %c", c);
Log("Integer       %i", i);
Log("Unsigned      %u", u);
Log("Long          %l", l);
Log("uNsigned loNg %n", n);
Log("heX           %x", x);
```