Add rudimentary support for .java, .html, .properties files

[daniel-beck]

Mostly fixes #1.

Identifies:

• https://github.com/jenkinsci/workflow-support-plugin/blob/f8d41ac42279d1811b81b0afb5e6e2e4b95843fe/src/main/java/org/jenkinsci/plugins/workflow/support/steps/input/POSTHyperlinkNote.java#L86 (the test case)
• https://github.com/jenkinsci/jenkins/blob/e1a6b190d4d71e95a8e00facd52ce7718909b9e8/core/src/main/java/hudson/util/ListBoxModel.java#L73-L75 (OK to find IMO)
• https://github.com/jenkinsci/collapsing-console-sections-plugin/blob/5685b78d0defbe4783f82d4dcf68bc1bde63f327/src/main/java/org/jvnet/hudson/plugins/collapsingconsolesections/CollapsingSectionAnnotator.java#L107 (for False negative in collapsing-console-sections-plugin #11)

… and a bunch of stuff in test sources.

[basil]

This is working pretty well for me, but I'm getting some errors in plugins with .properties and/or .html files that aren't UTF-8 encoded, such as credentials and subversion. As of jenkinsci/jenkins-test-harness#433 we can guarantee that .properties files are either UTF-8 or ISO-8859-1. I think it would be best to try UTF-8 first and fall back to ISO-8859-1, and then error if neither work out. I can help contribute the code for this if desired.

[daniel-beck]

As of jenkinsci/jenkins-test-harness#433 we can guarantee

Nice, that should be easy to do.

[basil]

Working well for me at the latest revision.