Make Java a required dependency

webodf.js needs it for closure compiler, and there is not much in the repo
which really makes sense to build without also building webodf.js
Remove old no longer used build target "zip"
install wodo.texteditor code files separated in zip subdir wodotexteditor/

also no longer install wodo.texteditor-only ones in programs/editor
Add parameter to zipdir.js for setting a path prefix to zip entries
Use an unversioned directory to collect the files for wodotexteditor zip

(helps testing as the url to browse to in the build dir does not change all the time)