Document parts of FilePath.

FilePath was a little lacking in documentation, this documents getRemote,
createTempFile, createTextTempFile and createTempDir.

Conflicts:
	changelog.html

JENKINS-10432 - Adding wiped out workspace as a reason for no workspace

User has to choose a custom installation.
There are two choices:
- Start at boot as "daemon" (enabled by default)
- Start at boot as "jenkins" (disabled by default)

If user disables the first and enable the latter, the installer
will create a new user "jenkins" and new group "jenkins"
(if they do not exist), chown JENKINS_HOME to jenkins:jenkins
and set up launchd job to run Jenkins as "jenkins"

Also fixed some permission errors that PackageMaker complains about
when building the package.

Also PackageMaker xml file reformatted to be more readable

[JENKINS-11248] Build fails on "Deploy artifacts to Maven repository" due to trying to upload parent POM twice for release artifacts.

[JENKINS-12177] Zero executors on master is no longer valid

Fixed a bug in Winstone where a failure during request processing can
put Winstone out of sync with the next request.

Conflicts:
	changelog.html