nixos/gnome3: cleanup core-utilities

core-utilities is meant to be the base utilities for a GNOME system.

The following are removed and the gnome3 module will no longer include:
- accerciser
- gnome-nettool
- gnome-power-manager
- gucharmap
- nautilus-sendto
  See https://gitlab.gnome.org/GNOME/gnome-build-meta/merge_requests/246
- gnome-usage
- vinagre
- gnome-documents
  See https://gitlab.gnome.org/GNOME/gnome-build-meta/merge_requests/157
- dconf-editor
- gnome-todo
- gnome-tweaks
- evolution

The following were added:
- cheese
- geary