Add viewer program to created zip file, add special  CZip target

I propose to have on CI runs all the build products made available on the resulting page. Not only the products targetted at 3rd-party, but also benchmarks and browser tests which are usually only interesting to WebODF developers and possibly not part of release stuff. (Or should we also include benchmarks and tests in the created tarballs/zips? No idea, at least I have not yet seen unit test packages, but maybe I just did not search for it)

Currently the CI result page shows/links
* the localeditor
* the benchmarks.

The XPI is also available, but only by url-hacking right now. It seems the plan is to add it soon. The viewer is not yet available, because the used target in DEPENDS was wrong.

This PR adds the viewer plugin (but without a proper test document, any proposals?) to the created ZIP file. It does not yet add the tests (as those are not yet copied into the build dir to be used with the compiled webodf.js and I screwed up writing cmake code for that and it got late and I first want feedback now in general).

Additionally it adds a special CIZip target, which should be used in the future to create a ZIP file with all the files/products wanted for the CI, which might be more/different from the ZIP files intended for 3rd-party.

So please feedback on these questions:

Q1: What test document(s?) should be used for the viewer?

Q2: Should there be a separate CI ZIP product, or should benchmarks and tests also be put into the to-be-released single ZIP file? I would think No, but your experience might be bigger.