Add argument parser feature to the LSP.

[joewyz]

Description of changes:
Add the argument parser feature to the LSP and modified the Main class.

The argument parser will be able to parse the help and port-number arguments for now. For port-number argument, both flag argument and positional argument are supported.

Help print example:

Usage: java -jar smithy-lsp.jar [--help | -h] 
                                [--port-number | -p PORT_NUMBER] 
                                [<port_number>] 

Options for the Smithy Language Server:

    --help, -h
        Print this help output.
    --port-number, -p PORT_NUMBER
        The port number to be used by the Smithy Language Server. Default port 
        number is 0 if not specified.
    <port_number>
        Positional port-number.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.