General edits to the using poky and Extending Poky chapters.
I completed general edits to the second chapter of the poky reference
manual. These edits went from section 2.4.5 through the end of the
chapter. They consist of text rewrites for more active voice and follow
general technical writing principles.
I completed the same types of edits in the third chapter of the manual
from the beginning through section 3.3.2.
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
