Don't throw CertificateValidationException for all SSLExceptions.

An interrupted connection attempt to the server yields an SSLException
as well, like this:

E/k9      ( 6937): Caused by: javax.net.ssl.SSLHandshakeException: Connection closed by peer
E/k9      ( 6937):      at com.android.org.conscrypt.NativeCrypto.SSL_do_handshake(Native Method)
E/k9      ( 6937):      at com.android.org.conscrypt.OpenSSLSocketImpl.startHandshake(OpenSSLSocketImpl.java:302)
E/k9      ( 6937):      at com.android.org.conscrypt.OpenSSLSocketImpl.waitForHandshake(OpenSSLSocketImpl.java:598)
E/k9      ( 6937):      at com.android.org.conscrypt.OpenSSLSocketImpl.getInputStream(OpenSSLSocketImpl.java:560)
E/k9      ( 6937):      at com.fsck.k9.mail.store.ImapStore$ImapConnection.open(ImapStore.java:2459)

We don't want the user to notify of 'certificate problems' in that case.
Fix it by checking whether the SSLException was actually triggered by a
CertificateException.
Merge pull request #513 from maniac103/fix-cert-exception-handling

Don't throw CertificateValidationException for all SSLExceptions.
Add Lollipop lock screen notifications.

Add vector versions for some notification icons (yay Illustrator)
Add comments reminding people to add their settings to GlobalSettings.
<plurals> support for notification_new_messages_title
Not sure why #ffffffff is resulting in black with targetSdk 17.