Make arguments for -At and -Wt parameter optional

[sparkhi]

In the documentation for the CLI, we mention that:

You can also specify individual archive types you want to process using -At and -Wt, followed by the types you want to process. Any not specified will not be processed:
e.g. droid "C:\Files\A Folder" "C:\Files\A File" -R -At zip 7zip -Wt warc
If you don't want to expand any archive types, then just use the -At or -Wt options with no archive types specified.

It appears that we treat the -At flag as optional but, if the parameter is specified then the arguments for it are not optional. As a result if someone uses just -At parameter, they experience an error message.

The -At and -Wt parameters should be changed such that arguments should be optional