Make sure that change log annotation cannot result into exception

Although javadoc for ChangeLogAnnotator#annotate() states that any exception should be caught in this method and it should return normally, some implementation don't respect it or e.g. in case of missing some dependecy (resulting into NoClassDefFoundError) plugin itself can hardly ensure that no exption is thrown. We should ensure it on the core level.
[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]
Typo.
Changed Javadoc according to jglick's recommendation
Fixed typos in French translation

- "systême" --> "système" (5 times)
- double quotes
Merge pull request #670 from olivierlemasle/master

Fixing typos on French translation (in the "Administrer Jenkins" page)
[JENKINS-16341] Amelioration of memory leak by at least interning some heavily redundant strings.
Merge branch 'master' of github.com:jenkinsci/jenkins
Use request protocol for configured Jenkins url
[JENKINS-16342] Improving responsiveness of asynchPeople when Gravatar plugin is in use.
This change does not necessarily improve total performance, since the avatar is still computed.
But (1) the computation is correctly done in the work thread, not in the HTTP response thread;
(2) the computation is done just once for a given User, which could reduce load when many AJAX checks are done.
Added bug number to the test
Add changelog record for pull #671
Merge remote-tracking branch 'jenkins/master'
Merge pull request #650 from vjuranek/changelog_except

Make sure that change log annotation cannot result into exception