Update messages

Fix typos and adjust messages to always begin with upper letter.

Signed-off-by: Aline Manera <alinefm@linux.vnet.ibm.com>
Update po files according to Transifex translations.

Also remove all translations from English po as it does not needed to be
translated.

Signed-off-by: Aline Manera <alinefm@linux.vnet.ibm.com>