Eliminated the wrong script tag generation from <st:bind/>

Integrated bytecode-compatibility-transformer that allows core to
do signature changes on properties that plugins might depend on.

The library performs necessary bytecode transformation to achieve this.

The first use of this is to fix plugins that looks for List
AbstractProject.triggers, thereby resolving JENKINS-18677.

For the time being, I'm not loading such compatibility annotations from
plugins, but I did code that in PluginManager. Let's see how this
feature work out for a while in the core, and if it looks stable and
solid, we'll open it up to plugins at that point.

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

Do not use anymore shaded version of wagon-http as it we can control commons-logging version

This page gets displayed when we throw an unhandled exception.

The exception handler ended up adding almost all the headers again,
resulting in a lot of duplicate headers.

Most critically, stapler was adding "Content-Encoding" header twice,
breaking browsers.

This version supports piping of stdout/stderr directly into
OutputStream, avoiding the need for running a thread to pump the stream.

Integrated the new version of Stapler that fixes them.