TC awareness

[jole78]

make deploy aware of TeamCity.

function Configure-ExecutionContext {
    if($Env:TEAMCITY_DATA_PATH) {
        $Script:OnDeploymentStarting = [System.Action] { Write-Host "##teamcity[progressStart 'deployment in progress...']" }
        $Script:OnDeploymentFinished = [System.Action] { Write-Host "##teamcity[progressFinish 'deployment in progress...']" }
    } else {
        $Script:OnDeploymentStarting = [System.Action] { Write-Host "deployment started" }
        $Script:OnDeploymentFinished = [System.Action] { Write-Host "deployment finished successfully" }
    }
}