Design:
- Move CheckExtensionType() to ExtensionManager
- Renaming Thumbprint to CertificateThumbprint
- Removing ServiceName from New- cmdlets

Re: Review:
- Remove ConvertToSecureString() and use namespace
- Refactor Get- cmdlets' Linq queries
- Redundant code in ExtensionRole

Apply fixes:
- Should not upload certificate in the new- cmdlets
- Config builder in New-/Set- Deployment should continue to add new config context