Making SD card progress!

I've made more progress on talking to the SD card.  I've now completely finished the initialization sequence and am in transfer mode and ready to start multi-block writing.  That will be my next task when I work on this again.

I've also beefed up the logger.  It is really inefficient but still meets my timing constraints so I am pleased.  Here is what the logger spits out.  My comments are in italics.

- Reset

C00 go idle

C08 notify SD card that we're using 3.3V and we can support newer commands

C55 get ready to send ACMD41

A41 initialize

C55 initialization is busy, so we keep looping until it's ready

A41

C55

A41

C55

A41

C55

A41

C55

A41

C55

A41

C55

A41

C55

A41

C02 get SD card's CID

C03 get SD card's relative address

C07 select this SD card for transfer mode

C13 get current status

C55 get ready to send ACMD6

A06 switch into 4-bit (wide) data bus instead of 1-bit data bus

C06 switch from 25 MHz to 50 MHz (ie "high speed" mode)