Added "AutomationSettings.CommandInterval" property

This is a useful feature, where the speed of command playback can be modified within a recorded XML file. This has helped in spotting issues with a recorded test case, when the command playback slows down to inspect the behaviors. This change has been validated with unit test cases under "RecordedTests.cs" to work with existing command XML files (which do not have the "CommandIntervalInMs" attribute). So the change is safe.