docs/library/uio: Update for Pycopy, elaborate docs.
docs/library/uio: Update for Pycopy, elaborate docs.

Clarify various points and grammar.

Change-Id: I978628dbb14b6ebe526ed39d0b4f20a8b835edb1
Signed-off-by: Paul Sokolovsky <9dc5061f178bb11813e14f1ed02ba27eaf21fa5d@users.sourceforge.net>

pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython