Allow override of input parameters

[Sarafian]

To help install as template, some parameters are best that they are overrider in Install-ISHDeployment.ps1

$inputParameters=@{
machinename="mock"
baseurl="mock"
}
& .\Install-ISHDeployment.ps1 -InputParametersOverride $inputParameters

Script needs to use these values either by replacing the xml nodes or by creating new ones.

[beutepa]

Tested for v13.