Validate CLI commands

As a user, I'd like to have as intuitive commands in the installer as in any other command line tool. We need to validate that the commands are intuitive, commonly used, and user friendly. One way to do this is to validate the commands against other package managers. 
 

Results

Some problems I spotted

--version Displays version information.
--framework-version Displays the version of the Qt Installer Framework.

The difference between these two is a bit unclear. If we really need the second one, I'd suggest to rename it to something like "--version-number".

--proxy Use system proxy on Windows and Linux. This option has no effect on macOS.
--no-proxy Do not use system proxy.

I think we should add a "default" mark here. Or even remove the first option. As far as I know, this is a common behavior to use a system proxy by default if this is available.

--checkupdates Check for updates and return an XML description.
--updater Start application in updater mode.
--manage-packages Start application in package manager
mode.

These don't work. I think it would be better to add better explanation why and what I should do to make them work.

--squish-port <port number>

This option is probably not related to the main installer functionality and shouldn't present in the release mode at least.

--addRepository <URI,...> Add a local or remote repository to the list of user defined repositories.
--addTempRepository <URI,...> Add a local or remote repository to the list of temporary available repositories.
--setTempRepository <URI,...> Set a local or remote repository as temporary repository, it is the only one used during fetch.
Note: URI must be prefixed with the
protocol, i.e. file:///, [https://|https:],
http:// or [ftp://|ftp:].

These look a bit inconsistent with other names. We should use something like "
--add-repository" for example. Ditto for other camelCase commands. + we need to add shortcuts, i.e. "
--add-repository, -ar"

What to replace/extend

--available-packages <regexp> -> search, se (if a package is installed there should be a symbol indicates it)
--update + --update-packages <package,...> -> update, up (updates all packages or only packages specified)
--installed-packages -> list-packages, lp or list-installed, li or just "list"
--install-packages <package,...> -> install, in
--uninstall-packages <package,...> -> remove, rm (if no packages specified, removes all installed packages after a confirmation)
--target-dir <directory> -> install-root, ir or root, r

What to add

--remove-repository, rr
--list-repositories, ll
optionally, other repos-related actions (modify, check, rename, etc.)

--clean, cc – drops local caches (any other leftovers)