Add support for delete confirmation in message list

Fixes issue 6260
Merge pull request #470 from k9mail/issue_6260_delete_confirmation_in_message_list

Add support for delete confirmation in message list
Issue 3559: Use From or ReplyTo hostname in Message-ID if available.

I wrote this fix to avoid obviously specifying that I am using a mobile device
to reply to an email.

Others want this for ease of filtering messages from their host by Message-ID.
Issue 4690: Add privacy pref to omit K-9 User-Agent header.
Issue 6372: Add preference for setting timezone to UTC.

This is a privacy preference to avoid leaking your current location while
replying to email.
Fixes for cketti's code review on pull req #472

Leave the hostname == null checks so we can fall back if a hostname is not
found. Also convert message-id to upper case to match Apple Mail (for
privacy).
Merge pull request #472 from mikeperry-tor/improve-header-privacy

Improve header privacy (Issues 6372, 3559, and 4690)
Use latest Gradle Android plugin and build tools
Fix 'testsOnJVM' Gradle task
Remove ActionBarSherlock
Updated Japanese translation of the changelog.
Merge pull request #476 from k9mail/remove_actionbarsherlock

Remove ActionBarSherlock
Fixed https://github.com/typingArtist/k-9/issues/1. HELO/EHLO IPv6 address literals
are now conforming to RFC5321.
Merge pull request #478 from typingArtist/master

Fix: HELO/EHLO with literal IPv6 address not conformant to RFC5321
verified in spec – ashleywillis
Update providers.xml

Added apple mail providers (apple.com, mac.com, me.com, icloud.com)
Sort apple emails in own category and add icloud.com
 Sort apple emails in own category and add icloud.com
Fix indentation
Merge pull request #481

Sort apple emails in own category, add apple.com and icloud.com
Use latest Gradle Android plugin and build tools