Fix Profile authentication, normalize Environment cmdlets

[markcowl]

• Enables authenticating using the New-AzureProfile cmdlet and keeping the tokens in the current session
• Enables creating empty profile
• Allows Add- and SetAzureEnvironment cmdlets to manipulate all environment values
• Allows piping Environment objects
• Allows using Environment objects resulrned by Get/Set-AzureEnvironment to New-AzureProfile
• Fixes Service principal authentication fails in Azure Automation #655
• Fixes New-AzureProfile throws error when used with a ServicePrincipal #332

[markcowl]

@azuresdkci retest this please

[markcowl]

http://azuresdkci.cloudapp.net/view/1-AzurePowerShell/job/powershell-on-demand/89/

[markcowl]

http://azuresdkci.cloudapp.net/view/1-AzurePowerShell/job/powershell-msi/411/

[markcowl]

http://azuresdkci.cloudapp.net/view/1-AzurePowerShell/job/powershell-msi/411/console

[markcowl]

merging as all tests pass and has been reviewed