Added support for VM extensions, static IPs, specification of arbitrary vm sizes and reserved IPs.

This PR contains changes for support for VM extensions, static IPs, specification of arbitrary vm sizes and reserved IPs.
same comment as above.

Please see: https://github.com/Azure/azure-sdk-tools-xplat/blob/dev/lib/commands/asm/site._js#L467
                    https://github.com/Azure/azure-sdk-tools-xplat/blob/dev/lib/commands/asm/site._js#L194