Add XML support to en/disable stacktrace package detail

This prevents developers from attempting to modify event's mdc map. For example by invoking

event.getMDCPropertyMap().put("k", "v");

This fixes LOGBACK-1063 by ricochet.

with the latest version the release process fails

Changed the default enable status of packaging info in stacktraces
to be disabled to avoid the expensive lookup unless requested.

Added an XML attribute "packageTrace" to <configuration> in order to
allow enabling or disabling the packaging info in stacktraces. When
the attribute is omitted, the default setting is assumed (disabled).

To enable package detail in logback.xml:

  <configuration packageTrace="true">
    ...
  </configuration>

LOGBACK-730
LOGBACK-966

LOGBACK-1046 fix suggestion

Documentation: Fix <h3> tag issue

[LOGBACK-540] Filtering out selected stack trace frames

Plugin and dependency updates plus add missing overrides in logback-access

for users using eclipse with annotation scanning turned on.

janino to 2.7.8
groovy to 2.4.0
tomcat to 7.0.59

maven-gpg-plugin to 1.6
maven-javadoc-plugin to 2.10.1
maven-jxr-plugin to 2.5
maven-bundle-plugin to 2.5.3
findbugs-maven-plugin to 3.0.0
maven-source-plugin to 2.4
maven-release-plugin to 2.5.1
maven-dependency-plugin to 2.10
maven-jar-plugin to 2.5
maven-surefire-plugin to 2.18.1
maven-site-plugin to 3.4
maven-install-plugin to 2.5.2
maven-deploy-plugin to 2.8.2
maven-compiler-plugin to 3.2
maven-clean-plugin to 2.6.1
wagon-ssh to 2.8

Add comment about maven-resources-plugin 2.7 as it errors currently if
upgraded.

This plugin is likely to be soon removed from maven and preference is to
use m2e for such items.  This is not needed for any modern eclipse
version.

Make AccessEvent.prepareForDeferredProcessing() to create a copy of the ...

It was a mistake to use original httpRequest as long as it is available because web containers may recycle it and populate with the fields from another request. So make sure that when prepareForDeferredProcessing() is called, we will be only using copied data.

Make AccessEvent.prepareForDeferredProcessing() to create a copy of the request attributes map so attributes are available later even if processing is done in a background thread.

Only Serializable attributes are copied to be on a safe side. Also, do not copy attributes set by Logback's TeeFilter as the very same information is already serialised as request/response content.

LOGBACK-929: daemonized threads created by logback executor service.