Implements #67

Implements #66

Implements #65

When disabling the "keep dns cache" feature when the VPN is not running, and then enabling it when it already is running won't clear the table of cached responses but the app is going to try to persist the current cache. If an entry of the current cache was already in the database the app crashed with a failing constraint. As a fix, clear the database before inserting the current cache.

Fixes #63

Bump fdroid version to 1.0-Beta (Build 31)

Implements #61

Bump fdroid version to 1.0-Beta (Build 30)

Implements #59

Implements #58

Implements #57

Resolve "Add Sentry to log exceptions"

Closes #56

See merge request !14