[JENKINS-16215] Avoiding unnecessary downloads in FilePath.installIfNecessaryFrom.

The updated version uses the locally cached timestamp, '.timestamp', to set the
'If-Modified-Since' header. 304 Not Modified responses are dealt with by
aborting the installation.
Add regression test for SurefireArchiver test mojo detection [JENKINS-8334]
[FIXED JENKINS-8334] use heuristics to detect test-mojos instead of relying on hard-coded plugin names
Additional testcase
Record start time of mojo execution in MojoInfo and use that information
to determine which test result files belong to the mojo execution
Use old method to find report files for a mojo. New method still needs some more testing.
Refactored detection of test mojos to simplify SurefireArchiver class [JENKINS-8334]
[FIXED JENKINS-16278] Fixed RememberMe cookie signature generation (bugfix on SECURITY-49)

New cookie signature generation was not implemented in creation of RememberMe cookie, but only in its verification.
Fixed by new override TokenBasedRememberMeServices2.loginSuccess
Diagnostics in case builds directory is unreadable.
A user running 1.467 reported:
java.lang.NullPointerException
    at hudson.model.RunMap.load(RunMap.java:216)
@since associated with JenkinsRule.
Merge pull request #668 from kutzi/maven-testmojo-heuristic

Use 'duck-typing' approach for detecting test mojos
Changelog and cleanup for [JENKINS-8334]
Merge pull request #660 from larshvile/master

 [FIXED JENKINS-16215] Avoiding unnecessary downloads in FilePath.installIfNecessaryFrom
[JENKINS-16215] : changelog
Added serialVersionUID to all Callables
to build=bauen, but for 'Build' there's no good short german translation
Minor German translation updates
[FIXED JENKINS-16319] Stream ordering problem prevented SecretRewriter from working on Windows.
[JENKINS-16273] Improved instructions for passing -jnlpCredentials.
First, display instructions when the user has CONNECT, not necessarily ADMINISTER.
Second, when anonymous users cannot CONNECT, show how to use -jnlpCredentials
(and do not bother showing javaws, since it does not work in this case).
[JENKINS-16444] Diagnostics useful for this and similar exceptions during Jelly evaluation.