Merge branch 'maven-3.1.0' for maven 3.1.0 support in Maven Integration Plugin

Unclear what Run.getEnvironment is supposed to return after the build is complete.
In particular, SubversionSCM calls this during polling to substitute variables in e.g. repo URL.
Presumably in such a case node-specific variables such as ToolInstallation.home would be irrelevant.
But in general should this reflect the “current” computer (if any), or the computer on which the build ran?

[FIXED JENKINS-18898] ToolInstallation.getHome may be null, and buildEnvVars must take that into account.

Fix javadoc for QueueTaskDispatcher and NodeProperty

Fix javadoc for @see reference in MatrixAggregator

Fix SCMTriggerCause javadoc to deprecated constructor

Fix javadoc link in MatrixExecutionStrategy

Uses the outer class plus the inner class to name the argument, which
satisfies javadoc.

There is a BuildableItem interface in hudson.model, but the references
in these files to BuildableItem objects are refering to an inner class
of the Queue object, not to the interface defined in huson.model.  The
javadoc link improvement may help authors see that difference.

http://javadoc.jenkins-ci.org/hudson/matrix/MatrixAggregator.html#startBuild()
has an @see reference which should be a link.

http://javadoc.jenkins-ci.org/hudson/triggers/SCMTrigger.SCMTriggerCause.html
includes a deprecated constructor with an @{link } reference to the
preferred constructor.  That link is broken in the current javadoc.
This fixes the broken link.

Fix javadoc link from deprecated DumbSlave constructor

See https://groups.google.com/forum/#!topic/jenkinsci-dev/yf8i1v5XSDg

Clearer display of log messages: chronological order, and coloration of repeated vs. fresh metadata.

Fix ComputerListener.onTemporarilyOffline javadoc to match implementation ...

Remove javadoc reference to now private buildReactorListener

Fix several @link javadoc warnings