Added freeform string input on command line

[Baldanos]

This patch adds the possibility to write strings in the command line that will be converted to their ASCII counterpart before being sent on each protocol :

> uart 
Device: UART1
Speed: 9600 bps
Parity: none
Stop bits: 1
uart1> "Hello world"
WRITE: 0x48 0x65 0x6C 0x6C 0x6F 0x20 0x77 0x6F 0x72 0x6C 0x64 
uart1> 0x01 "A" "B" 0x2:2
WRITE: 0x01
WRITE: 0x41
WRITE: 0x42
WRITE: 0x02 0x02 
uart1> test
WRITE: 0x74 0x65 0x73 0x74 
>