reenable sorting by sender in messagelist

This was disabled in faa666394ce0bf9e4239869ee194991d2f3308f1
because it isn't possible to extract the name of the android
contact in the 'ORDER BY...' clause when querying the database.
Instead it simply sorts by the email address.

This may cause the same contact to appear multiple times in
the list, if they have multiple email addresses assigned.

But in most cases this is good enough and surely better than
not having the option to sort by sender at all.

Desktop mail clients such as Thunderbird also simply use the
sender email information when sorting the column.

This also adds a SenderComparator for usage in the MergeCursor.
Update strings.xml
Update German translation.
Make the label on the "mark read" action on Jelly Bean notifications less confusing
Merge pull request #290 from rk4an/master

Update French translation
Fix typo in German translation.
Merge pull request #293 from justdave/notification_mark_read

Make the label on the "mark read" action on Jelly Bean notifications less confusing
Remove explicit left-alignment so EditText works with RTL languages
If messagelist started from Unified localsearch, verify if we are really dealing with multiple accounts. If not then set SingleAccountMode anyway.
Update message_compose_reply_header_fmt to have only one newline

The PREFIX quote style was using an empty line between the header and
the quote. But mail apps using this way of quoting style do not have an
empty line between the quote header and the quote.
Fix settings file versioning
Better cope with messages having identical message IDs
Avoid NullPointerException
Avoid another NPE
Don't show ALL unread messages for "notification opens unread messages"
Hide "condensed layout" setting instead of disabling it
Change smtp+tls default port to 587.
Always enable "pull to refresh" when "check mail" action is shown
Fix copyOrMove() so it works for single messages in Unified Inbox
Exclude folders Trash, Spam, and Outbox from "All messages"