documentation/poky-ref-manual: changes applied from a patch submitted by Cyril Humbert.

documentation/poky-ref-manual:  changes applied from a patch submitted by Cyril Humbert.

Cyril submitted a patch via email form for several spelling corrections.  The master docs, however, are not up-to-date with what I have on my contrib area.  Many of Cyril's corrections were already addressed.  A few were not and I have updated them here with this commit.

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>