[FIXED JENKINS-18196] Change to the estimated duratrion calculation to prevent performance issues with lazy build loading

Poll on the last existing workspace instead of the last workspace,

Allow headless installs again

Since I don't think any other scripts depend on this one, I'm just giving it a low enough priority.

... with a test case. The fix is in Stapler.

Servers often want headless java to not install graphical packages
but the current depends force the install of non-headless java.

Now to check behavior in trunk.

[JENKINS-3265] [JENKINS-17341] Even if older plugins throw an NPE during reload, continue loading job.

which may be offline, or wiped.

removed the noAnime() conversions, so we can rely on the compiler to warn us, if we forget a case here

Add convenience method for checking if object is MatrixProject

[FIXED JENKINS-18671] Clock Difference broken on Manage Nodes page

against incorrect values if times are ever compared between different JVM nodes