ReadPixel is working (we hope)

This is a combination of stuff done by hellmann42 and myself that
appears to be working
Read/Write rectangles of pixels

Added in readRect and writeRect which takes an array and either reads in
that many pixels or writes that many pixels
slightly faster readRect

Experiment with faster readRect, which tries to keep the SPI queue full.
But issue with multiple rows, that I am still trying to figure out
Fix writeRect bug

Fixed the bug that when we wrote more than one row of pixel data, the
data got misaligned
Proposed fix for drawChar size>1 solid background

There is an issue of text being drawn that, when the size > 1 and we
have set the text background color, the top lines are overwritten.  This
is one fix, other fix would change loop at bottom of char...
try writeRect to display bitmap

I thought I would try out using the writeRect function I added to see if
it would speed up drawing the bitmap.  I have it alternate drawing,
using the old way and with writeRect.  Times did improve from: 1026ms to
787ms
drawChar Fix V2

Changed to work more like other drawChar branches and only update 8*size
vertical pixels per char
Merge pull request #1 from KurtE/master

Fixes to readPixel, drawChar + new readRect/writeRect