Cleanup qubes-dom0-update interface

[mirrorway]

Consider streamlining the procedure to upgrade, install, search, reinstall, list packages.

BEFORE                                                  AFTER
sudo qubes-dom0-update                                  qubes upgrade
sudo qubes-dom0-update <pkg>                            qubes install <pkg>
sudo qubes-dom0-update --action=search <pkg>            qubes search <pkg>
sudo qubes-dom0-update --action=reinstall <pkg>         qubes reinstall <pkg>
sudo qubes-dom0-update --action=repolist                qubes list-repos

You don't always use qubes-dom0-update to update anything, so "update" shouldn't be in the name.

Consider making it setuid root so you don't need to sudo all the time. Or reserve sudo for operations that modify the system.

Consider making qubes-specific package discovery easier. An awesome thing about qubes is being able to install entire preconfigured operating systems and even sets of operating systems (whonix) with a couple of keystrokes. To spotlight these inter-vm packages and also community contributions, consider making qubes list without arguments show these qubes-specific packages.

$ qubes list

 Official Qubes Repository (32)
------------------------------------------------------------------------------------------
 qubes-template-debian-9      1.0    Debian template
 qubes-template-fedora-26     1.0    Fedora template
 qubes-template-devel-26      1.0    Everything you need to build Qubes components and...
 anti-evil-maid               4.0.1  Keep away the evil maids
 ...

 Community Repository (152)
------------------------------------------------------------------------------------------
 qubes-template-whonix-ws-14  3.0.1
 qubes-template-aosp-sdk-7    1.0.1  Basic Android development environment
 qubes-template-steam-2       1.0.1  Install and play games. Requires a secondary VGA...
 qubes-template-android-x86   1.0    Run Android apps natively!
 qubes-template-reactos       2.1
 sys-pia                      1.1.2  vpn qube configured for Private Internet Access
 sys-i2p                      0.0b4  Connect to the I2P anonymity network
 kernel-linux-kspp-4.15       1.0a1  Hardened Linux kernel
 qubes-little-snitch          1.0    An interactive firewall that runs in sys-firewall
 ruddo-vpn                    1.0.3  
 logvm                        1.1    [GSoC 2018] VM that aggregates and preserves logs 
 unikernel-firewall           2.2.3  Resource-efficient alternative firewall 
 ...