Bug fixes, doc fixes, support for -passthru.

Includes -

Cmdlets

- Modify WAPack IaaS cmdlets to use common ExecuteCmdlet override provided by cmdletbase.
- support for -passthru on Set-WAPAckvm and VM lifecycle operations cmdlets.
- fixed the use of  property ValueFromPipeline .
- Help doc fixes.

Scenario Tests

- Moved WAPackIaaS Unit Tests to Commands.Tests
- Moved WAPackIaaS functional tests to Commands.ScenarioTests
- Re-factored a bunch of tests for supporting -passthru.
- Fixed flaky tests