[JEP-216] Extract localization support infrastructure into localization-support plugin

[daniel-beck]

Work in progress: localization-support is not yet hosted or released. Some commits need to be reverted before this is merged.

Downstream from kohsuke/localizer#16, jenkinsci/stapler#156, jenkinsci/jenkins#3729, and https://github.com/daniel-beck/localization-support-plugin

Also update the resource files with the current state from Jenkins core, as they're being removed in the PR linked above.

Later revisions of this PR also support webapp resources, both from plugins and from core. Examples:

Core webapp

Before

After

Plugin webapp

Before

After

(with placeholder resource)

[LinuxSuRen]

LocalizationFacet and I18nRequestDispatcher exists for help resource files. But it's not the best solution.

[daniel-beck]

@LinuxSuRen Got it. I just was confused because the help files were still in core, as well as in this plugin, so I thought this worked when it did not. There's quite a lot of duplication going on.

[LinuxSuRen]

@daniel-beck Actually it's working partially. So I did not remove those files from the core.

[LinuxSuRen]

@daniel-beck We should figure out a way to solve a similar situation. I found the exception earlier. He should send the message if someone made a change of localization key or parameters.

[daniel-beck]

daniel-beck/localization-support-plugin@492bb16 looks like it handles the problem of most localized help files.

The only ones still being a problem seem to be webapp/ resources.

[LinuxSuRen]

LGTM
They're all good except those help files were come from Descriptor. Like:

http://localhost:8080/jenkins/descriptor/hudson.ProxyConfiguration/help/port

But I think we can merge this. Then fix that later.

[daniel-beck]

@LinuxSuRen Thanks for identifying this problem, you're right.

It seems I originally did that in jenkinsci/localization-support-plugin@492bb16 but removed it again in jenkinsci/localization-support-plugin@a5b4e4f#diff-ba7f3e4f89111bd652dffe39ab80d9c7 because I didn't remember why it was needed.

Will fix in localization-support and integrate it here.

[daniel-beck]

@LinuxSuRen The PR linked in the latest commit should restore this functionality. Could you test the current state of this PR in depth? I expect all kinds localizations to be supported as it is, with the build of localization-support integrated in 8cf2438

[LinuxSuRen]

@daniel-beck Of course. I'll test this by manul.

[LinuxSuRen]

LGTM