[#111] Added info to avoid Sentry duplications (due to 3rd party Timber integration)

[ssawchenko]

Related Issue: #111

Summary of Problem:

https://docs.sentry.io/platforms/android/configuration/integrations/timber/

Starting from version 3.1.0, the Sentry Android Gradle plugin will automatically add the sentry-android-timber dependency. The plugin will only add the sentry-android-timber dependency if a timber dependency was discovered on the classpath.

This will cause our errors to be duplicated in Sentry.

Proposed Solution:

• Unfortunately the actual fix will have to be done in each of our client app's gradle files, however, this PR documents the required changes in the PR and shows how to do it in the sample app
• I have also updated the sample app a little to make it easier to test out sending only a single error (which makes testing duplication much easier)

Testing Steps:

1. Go to the Sentry page for the sample app: https://steamclock-software.sentry.io/issues/?project=5399932
2. Select all of the issues in the list and select the "Resolve" button; this should clear the list of errors and make it easy to see new ones coming in.
3. Run the sample app, and change the log level at the top to Release
4. Press the "Report Single Error" button
5. Wait ~10seconds (sometimes it may take longer to send the report to Sentry)
6. Refresh the Sentry page
7. Make sure you only see 1 error reported in Senty:
   

[phileo]

Tested, LGTM 👍