Work on docs

[Libor Polčák]

Hello all,

I prepared documentation for two wrappers for your comments. See 
https://pagure.io/JS-Shield/JS-Shield/c/f45091b985e3961fa6c0f94782fe7a99a8013f80.patch
 (or 
https://github.com/polcak/jsrestrictor/commit/f45091b985e3961fa6c0f94782fe7a99a8013f80)
 and 
https://pagure.io/JS-Shield/JS-Shield/c/4ef115fcd0979b4235b50be1bba47b2b57c6d62d.patch
 (or 
https://github.com/polcak/jsrestrictor/commit/4ef115fcd0979b4235b50be1bba47b2b57c6d62d).

I also improved the structure of the Doxygen documentation, you can see it at 
https://www.fit.vutbr.cz/~polcak/jsr/doxygen/html/index.html. Ricardo, Anna, I slightly 
modified the doxyfile, created DoxygenLayout.xml, and added "make docs" target 
to Makefile, see current master.

I know that each file still does not have authors and license info in the docs. 
Other than that, if you have any comment, please, let me know or provide a 
patch.

Commands \fn like "\fn fake_or_original navigator.geolocation.clearWatch" do 
not produce any output by Doygen. If anyone knows why, please, let me know.

Best wishes,

Libor