[cpackget] UX improvements

1. The overall verboseness of cpackget is very minimal. Perhaps making -v the default verbose option, and adding a new option for quiet working --quiet/-q would do the trick.

2. Since the installation may take quite long, it would be good to see progress on installing the pack. Is this possible? Example: Installing ARM.CMSIS.5.7.0 100% |████████████████| (<installed files>/<total number of files>)

3. Installing packs with packID without the version would print info messages I: Adding [ARM.CMSIS], where it could be more informative I: Adding [ARM.CMSIS.5.8.0]including the version, since cpackget would already know it by the time it prints out this message.

4. The help text shows up like cpackget [flags] cpackget [command], perhaps it could read cpackget [command] [flags]

5. cpackget should be able to handle SIGTERM and other forced termination cases. Just catching the termination intent and forcing cpackget to shutdown should be enough for now.

6. Running ./cpackget init generates the error message E: pack root not found. It might be better to display a more helpful message. Ex: E: No CMSIS Pack Root directory specified. Either the environment CMSIS_PACK_ROOT needs to be set or the path specified using the command line option -R, --pack-root string

7. Running ./cpackget.exe pack add ARM.CMSIS -R ./tmp-cmsis-pack-root/ with that pack being pre-installed, the error message is just E: pack already installed. It might be better to read something like E: Nothing done. The pack <vendor>.<pack>.<version> is already installed here: <cmsis_pack_root>/<vendor>/<pack>/<version>.

8. When running ./cpackget.exe index https://www.keil.com/pack/index.pidx -R ./tmp-cmsis-pack-root, nothing gets displayed, the download progress bar only shows up when the flag -v is specified. It’d be convenient to display it by default.

9. When re-running the command above, the error message shows like

A better error message would be E: The file 'index.pidx' already exists, use the flag '-f' to overwrite the existing file.