[FIXED JENKINS-17508] Artifacts not being deleted by LogRotator

[FIXED JENKINS-17681] Do not try to call resolveSymlink on a nonexistent link as you will just get an IOException, breaking peephole permalinks in some Windows environments.

[JENKINS-17681] Set up a test which passes on Unix but fails on Windows when symlinks are enabled on the platform but disabled for the current user.

(cherry picked from commit 4f0200a0)

[FIXED SECURITY-69] Require POST to redeploy artifacts.(cherry picked from commit 3e56c3fc)

[SECURITY-63] Check RUN_SCRIPTS for /eval.(cherry picked from commit 3d03990a)

[SECURITY-63] Require POST for running Groovy scripts.(cherry picked from commit 3bbb65df)

[FIXED SECURITY-67] Forbid CSS links in markup to be on the safe side.(cherry picked from commit 1e19eb3e)

No need to call isLoggable if you are only calling simply getters and relying on toString later.

[FIXED JENKINS-17775] Find (model) parent POMs properly during fingerprint recording at end of build.

TransferResource.getRepositoryUrl is documented to end in a slash if known, so we should not add one.
Parsing POMs
Downloaded artifact http://repo.jenkins-ci.org/public//org/jenkins-ci/plugins/plugin/1.456/plugin-1.456.pom
Downloaded artifact http://repo.jenkins-ci.org/public//org/jenkins-ci/jenkins/1.26/jenkins-1.26.pom

[JENKINS-17775] If MavenProject.getParent throws ISE during fingerprinting, report it but at least proceed.
Proper fix is to ensure that the model resolution uses the same environment as the actual build,
or is otherwise more lenient about finding the parent (e.g. enables plugin resolution).

[JENKINS-16845] Refinement to hotfix: if build field has already been cleared due to earlier warning, do not throw a new NPE.

This bug indicates that people are having trouble understanding who's
responsible for aborting the build. This change records that
information through the logger.