Add more icons and show different icon when application is u+x permission

[Scott Ritchie]

Binary package hint: gnome-exe-thumbnailer

To make executable applications visually distinct from regular files, we need:
A generic icon for Python .py
A generic icon for Java .jar
A generic icon for ELF (and Maybe FatElf)
A generic icon for shell scripts (.sh especially)
A generic icon for Wine .exe (already done, sort of)

Each of these should match the theme of the Wine one (which may be revised as well). Windows users will be familiar with the default program icon that looks much like it (looking like a small window with no content), so this already has a mental association with most users. In every case, these files when untrusted are going to be opened with executable-handler: https://wiki.ubuntu.com/karmic-wine-integration

It would also be nice if the icon looked something like executable-handler, which has yet to be visually designed.

We also need trusted versions of these icons. Once the file is given u+x permission it is presumed trusted. If it has an embedded icon (like Wine .exe files do), we should just show that. Otherwise we need to fallback on a generic icon, preferably one different from the untrusted version above so that the user isn't surprised when the app launches instead of executable-handler.