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.
Client Certificate Authentication
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
Merge branch 'master' into tls-client-cert-auth

Conflicts:
	src/com/fsck/k9/fragment/ConfirmationDialogFragment.java
Fixes needed after merging in master

Also, fix unit tests.
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
Clean up indentation

White space changes only.
Rework validateFields() and updateViewFromAuthType()

Previously, it was possible to have "Require sign-in" unchecked and a
"Security = None" setting for the outgoing server and still not be able to
tap "Next" because of a hidden (and irrelevant) "Authentication = Client
certificate" setting.

Check that the user has actually chosen a client certificate in
AccountSetupOutgoing.validateFields().

Also, there's no need to clear the password and certificate fields when
hiding them.  The user may accidentally change settings and want to change
them back without wiping out the existing settings.
Update providers.xml

Added apple mail providers (apple.com, mac.com, me.com, icloud.com)