simplification of SocketApender connection logic

LOGBACK-909 Fix race condition in SMTPAppenderBase

better fix for broken AbstractSocketAppenderTest

Update javadoc, cannot find CustomDBNameResolver

Fixed typo in configuration.html

AppenderBase started variable made volatile

AppenderBase started variable made volatile as it is mutable, access to it is not synchronized and it is shared between threads.
Fix for http://jira.qos.ch/browse/LOGBACK-1037

Fix for Prudent FileAppender and thread interruptions (LOGBACK-875)

Prevent logging on an interrupted thread from shutting down prudent file
appenders due to a FileLockInterruptedException

This reverts commit 147ed05b.

added missing unit test for re-establishing the socket connection when stream creation fails with IOException

fixed broken test setup for addsInfoMessageWhenEventIsBeingDroppedBecauseOfConnectionProblemAndDequeCapacityLimitReached

AsyncAppenderBaseTest: The appender was not allowed enough time to
flush the appender on #stop(), causing the empty-check of the appender's
queue to fail. The test appender's max-flush time is now extended from
30ms to >1000ms.

AbstractSocketAppenderIntegrationTest: A unit test expected
deque.takeFirst() to be called only once after a log-event is appended,
but the call actually occurs twice in a while-loop, where the second
call is intended to block, waiting for the next log-event.

AbstractSocketAppenderTest: A unit test that verified appender
behavior when its deque was at capacity neglected to fill the deque
before testing for errors.

Added note for LOGBACK-128

Add notes for #193 (LOBGACK-977), provided by Sebastian Gröbler

LOGBACK-977 - AbstractSocketAppender loses event for every socket connection break

extended documentation to reflect new SocketAppender behaviour towards synchronous/asynchronous queueing

* made AbstrackSocketAppender not lose events when socket connections gets lost (now uses LinkedBlockingDeque)
* extracted aspects of deque creation and output stream creation to factories in order to improve testability
* ecapsulated automatic flushing of output stream into a separate class in order to make this functionality testable
* slightly refactored internal structure of AbstrackSocketAppender to improve maintainability

Warn users against adding their release notes to news.html since that
always causes merge conflicts.