Dialogflow sample

[nnegrey]

Breaking multiple samples into individual PRs.
#108

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[nnegrey]

Kokoro Error: "File google-services.json is missing. The Google Services Plugin cannot function without it."

Since Android Studio now requires it to build the app, not sure how to get around this one.

[frankyn]

@nnegrey I might not be the right person to review this PR.

If the google-services.json is similar to a service account (I haven't taken a look). Take a look at this helper Groovy function.

android-docs-samples/nl/LanguageClient/app/build.gradle

Lines 60 to 67 in 30784ed

	task copySecretKey(type: Copy) {
	File secretKey = file "$System.env.GOOGLE_APPLICATION_CREDENTIALS"
	from secretKey.getParent()
	include secretKey.getName()
	into 'src/main/res/raw'
	rename secretKey.getName(), "credential.json"
	}
	preBuild.dependsOn(copySecretKey)

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