Networking Hybrid team minor but important PS changes

[Nilambari]

1. Added mandatory param to new dedicatedcircuit command let
2. Added Set / Remove default site command lets
3. Added new properties to return type of getconnection command let

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[hovsepm]

on-demand job: http://azuresdkci.cloudapp.net/view/1-AzurePowerShell/job/powershell-on-demand/311/

[markcowl]

@Nilambari It looks like network tests are failing - it appears that may be you need to upodate parameters in your powershell tests scripts to match these changes.

[markcowl]

@Nilambari Looks like there's still a parameter issue in the test scripts:

-------- System.ArgumentNullException : Value cannot be null.
Parameter name: billingType

[Nilambari]

Fixed the failing tests. Merge build is Passing now. Also, got on demand job:- http://azuresdkci.cloudapp.net/view/1-AzurePowerShell/job/powershell-on-demand/315/ successful.

Can you Please help merge this PR? Thanks a lot!

Thanks,
Nilambari