add a [geOrchestra instance] prefix to emails
Merge remote-tracking branch 'origin/master'
ldapadmin - improve email subjects
extractorapp - translate to English + plain/text

Note that some content is still in HTML (see https://github.com/georchestra/georchestra/issues/281#issuecomment-24091461).
ldapadmin - set the email templates plain/text and change redaction.
Merge remote-tracking branch 'origin/master' into issue278
fix #295 (first name and last name labels inverted)