Add 16x16 pixels icons to tde-guidance. #93

This is basically what we need for the Trinity Control Center to display the correct icon size for tde-guidance.

I've set this PR as rfc, I guess there other steps to register that change in the Deb packaging log (no ideas how to package stuff for Debian actually).

I never particularly liked when we use debian/rules to move icons around for installation (this is done in a few packages in fact). I think it would be better to dedicate a bit of extra effort and have those icons come up in /opt/trinity/share.... in first place, so we later can remove the extra rules in debian/rules. Same would apply to the existing 32x32 icons.
What do you think? (@SlavekB too)

Btw, similar work will be required for the ubuntu folder.

This PR is merely a way to drive your attention on this packaging weirdness.

I'l see if I can adjust everything in my PR for the cmake conversion, stay tuned...

As I see It, tde-guidance build setup and its packaging are both a pile of hacks, what are the reasons for these? I do not know, but I woudn't waste more time on them.

Work recovered, extended to Ubuntu and pushed.
Long term it would be good to check whether we cab simplify the rules files.