Adding a test and fixed a broken databinding (because of SCM vs Scm)

[JENKINS-13909] don't keep legacy *.hpi when uploading a plugin

Changes look good to me.

Add PluginManager.CONFIGURE_UPDATECENTER permission which allows a user to configure update sites and proxy info.

Ryan discovered an instance where Label cached data at incorrect state. I'm not sure exactly how this is caused, but it probably is some kind of data race.

Making it self-healing would hopefully eliminate this problem in practice.

I was getting IndexOutOfBoundExceptions on callStack.get() which means that there must be concurrent access (maybe via JS worker threads) => synchronize access to callstack

even jenkins takes care to load jpi first, this is confusing

Human readable size of files

Use Jenkins.RUN_SCRIPTS instead of Jenkins.ADMINISTER

Going beyond this requires CSS animation.

In particular, so that flashing animation gif uses transparent
background where possible.