debian packages: split package into client/server

debian/proxmox-backup-server.install

@@ -0,0 +1,9 @@
+etc/proxmox-backup.service /lib/systemd/system/
+etc/proxmox-backup-proxy.service /lib/systemd/system/
+usr/lib/x86_64-linux-gnu/proxmox-backup/proxmox-backup-api
+usr/lib/x86_64-linux-gnu/proxmox-backup/proxmox-backup-proxy
+usr/share/man/man1/proxmox-backup-proxy.1
+usr/sbin/proxmox-backup-manager
+usr/share/javascript/proxmox-backup/js/proxmox-backup-gui.js
+usr/share/javascript/proxmox-backup/images/logo-128.png
+usr/share/javascript/proxmox-backup/images/proxmox_logo.png