Integrate with PowerShell Help system [SKIP CI]

[shaominchen]

Integrate vDVS windows plugin installation script with PowerShell Help system.

Testing Done:

1. Print usage info if running script without any parameter:

PS C:\> .\install-vdvs.ps1
Usage: install-vdvs.ps1 [[-uri] <String>] [-uninstall]

2. Run Get-Help with this script

PS C:\> Get-Help .\install-vdvs.ps1

NAME
    C:\install-vdvs.ps1

SYNOPSIS
    Installation script for VMware vSphere Docker Volume Plugin.

SYNTAX
    C:\install-vdvs.ps1 [[-uri] <String>] [-uninstall] [<CommonParameters>]

DESCRIPTION
    This script helps to download, install, uninstall, and re-install VMware vSphere Docker Volume Plugin on your system.

RELATED LINKS
    https://vmware.github.io/docker-volume-vsphere/

REMARKS
    To see the examples, type: "get-help C:\install-vdvs.ps1 -examples".
    For more information, type: "get-help C:\install-vdvs.ps1 -detailed".
    For technical information, type: "get-help C:\install-vdvs.ps1 -full".
    For online help, type: "get-help C:\install-vdvs.ps1 -online"

3. Run "Get-Help -example"

PS C:\> Get-Help .\install-vdvs.ps1 -example

NAME
    C:\install-vdvs.ps1

SYNOPSIS
    Installation script for VMware vSphere Docker Volume Plugin.

    -------------------------- EXAMPLE 1 --------------------------

    PS C:\>./install-vdvs.ps1 https://bintray.com/vmware/vDVS/download_file?file_path=docker-volume-vsphere.zip

    -------------------------- EXAMPLE 2 --------------------------

    PS C:\>./install-vdvs.ps1 -uninstall

[venilnoronha]

LGTM