- Exec: provide arguments to 'pd-gui' so dragging files on the deskto icon launches Pd
- Categories: see https://specifications.freedesktop.org/menu-spec/latest/apa.html
  - replace the invalid "Multimedia" with "AudioVideo"
  - add "Development"
  - add "Music"
  - add "Graphics"
- Comment: slightly different wording with a couple of translations
- NoDisplay: drop the explicit setting to "false" (it's the default anyhow)

AppStream prefers the scheme: <tld>.<vendor>.<product>
and AppStream forces us to use the same id for the .desktop file as for the
 appstream metainfo.

so let's switch now, rather than later...

to be used by app-store like software, e.g. "gnome-software"

The same file is available as tcl/pd.xpm

Add Appstream metainfo and more

also add some more fields to the metainfo.
and use "Pure Data (Pd)" as the application name.

better than renaming...

fixups and automate installation of mimeinstall