Capitalize output messages

Some of the output/error messages were capitalized, some were
not. This patch capitalize everything for consistency sake. Other
minor changes were done to the messages like removing the superfluous
"error:" from die messages and adding a final period to messages that
were complete sentences as appropriate.

Signed-off-by: Eric Bélanger <snowmaniscool@gmail.com>
Signed-off-by: Pierre Schmitz <pierre@archlinux.de>