Keep the 4 icons we are using locally

This will make it easier to run on Mac / Windows than having to
install the whole tango-icon-theme to /usr/share/icons/Tango
Add icons used in camera and scan converter
Added icon files README, explaining license
Add real versions of icons that are symlinks

We should update the code to use these versions directly.
Merge pull request #5 from staldates/feature/keep-icons-local

Keep the icons we are using locally