Setup Wizard that asks for Doze Mode exception

Let's use this MR as an implementation ticket and discuss the details and copy here.

setup-wizard

For people that have Briar already installed or those that remove the whitelisting again, this dialog will appear:

Still to do:

• fix roboelectric tests
• find out why new gradle and Android Studio cannot resolve symbols of some libraries
• check if the battery optimization was revoked and if so request the exception again?
• merge !601 (merged) and rebase on it

Closes #1085 (closed), #1018 (closed)