[chat]added snackbar when chat private is exist

[hunght]

Please check you are not duplicating an existing pull request...

Changes

Add snack bar view. Navigating user direct to person chat view

Verification

If the user tries to create a new chat with a person, and there is already a chat with that person then:

1. Show warning Material Design "snackbar" saying there is already a chat with that person (auto disappear)
2. Open the chat with the person

[marknuzz]

Bitrise build: https://app.bitrise.io/build/5911c999aeda5da3 (passes)

[marknuzz]

Can you merge develop into this branch again @hunght so the launcher script is available during testing? Thanks!