update sources to qemu 2.0 - disabled patches

I will re-enable patches step by step in the following commits.

Bump version to 2.0-1.
refresh debian/patches/adjust-path.diff
refresh debian/patches/fairsched.diff
refresh and enable debian/patches/pve-auth.patch
enable vencrypt-auth-plain.patch
refresh and enable debian/patches/fix-qemu-img-snapshot-removal.patch
refresh and enable debian/patches/enable-kvm-by-default.patch
refresh and enable debian/patches/virtio-balloon-fix-query.patch
refresh and enable debian/patches/set-cpu-model-to-kvm64.patch
refresh and enable debian/patches/modify-query-machines.patch
refresh and enable debian/patches/modify-query-spice.patch
refresh and enable debian/patches/spice-use-pve-certs.patch
refresh and enable debian/patches/backup-add-vma-binary.patch
refresh and enable debian/patches/backup-add-vma-verify-command.patch
enable debian/patches/backup-vma-add-dump-config.patch
enable debian/patches/backup-vma-restore-tolerate-a-size-difference-up-to-4M.patch
refresh and enable debian/patches/backup-modify-job-api.patch
refresh and enable debian/patches/backup-add-pve-monitor-commands.patch
refresh and enable debian/patches/backup-add-dir-format.patch
refresh and enable debian/patches/backup-do-not-return-errors-in-dump-callback.patch