Add notes for LOGBACK-768 and LOGBACK-928

LOGBACK-768 Documentation: Fix mistake in the definition of the combined log format (missing brackets)

Add note for pull request #136 (LOGBACK-885)

Add note for pull request #156

Add notes for LOGBACK-926 and LOGBACK-904

LOGBACK-926 Update SyslogAppender to set the maxMessageSize to be the system default UDP size to prevent logs from being dropped if they are too large.

"<includes>" should've been "<include>"

We were null-checking the current status manager instead of the one
passed in.

This prevents a NullPointerException from being thrown, and allows the
socketNodeClosing method to be called for the SocketNode.

The constructor creates an ObjectInputStream, and this blocks until the stream
header is received from the client.

If the client doesn't send a stream header, construction of the SocketNode will
hang, preventing SimpleSocketServer from accepting new clients.

This change moves the construction of the ObjectInputStream into
SocketNode.run. As SimpleSocketServer runs this method in a new thread, a rogue
client won't prevent subsequent ones being able to connect.

Fixed issue "Failed to instantiate LoggerContext" because of " java.lang.SecurityException: AccessController.checkPermission is unsupported." (LOGBACK-760) using the solution provided in the comment by ori.

amendment for LOGBACK-644: suppress errors for nonexistent resource includes

* changed direct access of timestamp field to use getTimstamp() instead inside of calculateElapsedTime.

* Added support to the tomcat Server adaptor for correctly getting request start time. (Includes additional dependency on tomcat-coyote)
* Update layouts.html to document the addition of elapsedTime/D to the pattern support for IAccessEvent
* Modified AccessEvent.java to calculate the elapsedTime at construction of the event, instead of repeatedly in the getter.  This allows the value to be more easily seen in a debugger, and cleans up the code slightly.

Truncates multi-line subjects to the first line to prevent an SMTP error.

fixes #147

detachLoggerContext removes LoggerContext from ContextSelector. BUT
context.getLogger will create it again. So it's much more proper to
log at first and detach context after that.

fixes #51

Fix for LOGBACK-754

A NullPointerException occurred when setting a JUL logger's level to
null, which should have reset the logger level to the parent's effective
level. The null level was incorrectly propagated to context listeners,
leading to the NPE.

This patch propagates the logger's parent effective level.

Support suppressed exceptions

Check already exists inside called method

LOGBACK-832 - set parent classloader to avoid janino classes not being found

Use new instance of RecoveryCoordinator in each test. Otherwise, the timestamp
of the next call to isTooSoon() could happen well after the backoff threshold
on slow machines (such as small nodes on Cloudbees Jenkins), causing false
test failures.

This also renames and refines the individual tests.