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.
Don't show a disabled preference if there is nothing a user can do to enable it.
Issue 4503: Auto-fit messages option

Create a preference option to automatically shrink messages
to fit the screen width (default setting is "shrink").
Correct preference version number.

New number should match updated Settings.VERSION
Fix indentation
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.
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"
Use very light grey instead of white for message text in dark theme
Use a dark startup animation
Change SMTP default port to 587
Merge branch 'smtp_port_fix'
Merge branch 'message_compose_reply_header_fmt-update'
Merge branch 'better_singleaccount_check'
Merge branch 'message-list-sender-sorting'
Revert "Don't show a disabled preference if there is nothing a user can do to enable it."

This reverts commit 0ecc49815f1b90f57a8040254bda0faa3eb46a47 because
an equivalent commit was subsequently made to master:
5f49195a0a39f573e6728277ddf711fdcb26de87
Fix crash on Android 2.x caused by the "flicker" fix