feat: add cli option to generate shell auto completion

The urfave/cli/v2 has built-in auto-completion support for bash.
This enables generating the auto completions with a cli option
that can be added to environment setup scripts.

Also adding some distro support scripts for rpm and deb for the
auto completion setup.

To enable auto completion in zsh, this still needs to be added
to user .zshrc:
fpath=(/usr/share/zsh/site-functions $fpath)
autoload -Uz compinit && compinit

Fixes #2015

cmd/versitygw/main.go

@@ -146,7 +146,8 @@ func main() {
 
 func initApp() *cli.App {
 	return &cli.App{
-		Usage: "Versity S3 Gateway",
+		EnableBashCompletion: true,
+		Usage:                "Versity S3 Gateway",
 		Description: `The Versity S3 Gateway is an S3 protocol translator that allows an S3 client
 to access the supported backend storage as if it was a native S3 service.
 VersityGW is an open-source project licensed under the Apache 2.0 License. The