Fix issue 6269:  IMAP LOGIN failure

Some IMAP servers are broken and don't correctly handle string
literals with the LOGIN command.

This switches to using quoted strings instead.

This is what Thunderbird does.
Rework handling of certificate errors while pushing

Eliminate import of MessagingController in ImapStore.
Use the mApplication field in lieu of K9.app
Change POP3 error response detection

Instead of interpreting a "-" at the beginning of a line as
an error response, consider the absence of a "+" at the
beginning of a line as an error response.

This is what Thunderbird does.

http://hg.mozilla.org/releases/comm-esr24/file/55e96a433bd1/mailnews/local/src/nsPop3Protocol.cpp#l1177

The problem arises with godaddy servers spewing additional
lines of data upon login failure.  The login was being
interpreted as successful, and a STAT commanded was subsequently
being sent, resulting in a dialog saying 'Cannot connect to
server. (Invalid int: "auth_error:")'.

$ openssl s_client -quiet -crlf -connect pop.secureserver.net:995
...
+OK <24984.1394317012@pop.secureserver.net>
user testuser
+OK
pass testpass
testuser not found in the auth database
warning: auth_error: authorization failed (no such object)
-ERR authorization failed  Check your server settings.
Build plugins and tests with SDK 19
Include send failures in the K9mail-errors folder