Acra-5.5.0

• switch to androidx
• #768 allow to pass extras to sender
• new module acra-core-kts with kotlin convenience methods, e.g.

        initAcra {
            setBuildConfigClass(BuildConfig::class.java)
            setReportFormat(StringFormat.JSON)
            plugin<HttpSenderConfigurationBuilder> { 
                setHttpMethod(HttpSender.Method.POST)
            }
        }

can replace java-style builders and ACRA.init()