Remove use of Datadog RUM

[atavism]

For https://github.com/getlantern/engineering/issues/463

[jigar-f]

@atavism If we are removing datadog, Can you also remove datadog folder on kotlin

[atavism]

@atavism If we are removing datadog, Can you also remove datadog folder on kotlin

Done

[jigar-f]

@atavism Can we also remove this from Gradle

def ddApplicationID() {
    def value = project.getProperties().get("ddApplicationID")
    if (value == null || !value?.trim()) {
        return "\"\""
    }
    return String.format("\"%s\"", value)
}

def ddClientToken() {
    def value = project.getProperties().get("ddClientToken")
    if (value == null || !value?.trim()) {
        return "\"\""
    }
    return String.format("\"%s\"", value)
}

[atavism]

Can we also remove this from Gradle ...

@jigar-f, done!