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

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

Fix many of the javadoc unresolved @link warnings

Earlier javadoc for onTemporarilyOffline copied onTemporarilyOnline.

Fix javadoc tag which was not closed, remove ignored @author tag

Remove empty @return javadoc tags - add no value

Fix javadoc warnings in method parameters

Fix malformed @see javadoc reference

Can use source code history to locate original author.

Javadoc fixes for Jenkins core

@sine -> @since

@lnk -> @link

@author: -> @author

Make embedded @ sign literal in one case where it is literal

Fix small typo

Also ensuring that Jenkins configuration is saved after new XML is POSTed.