Support Android API 21-23

[natsuk4ze]

CompletableFuture in java8 is not available for Android API less than 24 and will crash.

completed:

• [x] open()
• [x] hasAccess()
• [x] requestAccess()
• [x] putImage()
• [x] putImageBytes()
• [x] putVideo()
• [x] add tests

[natsuk4ze]

I am sure that is the cause. However, I would consider migrating the native Android code from java to kotlin.

[natsuk4ze]

Now test-fix is settled, I'm bcak to this.