requires new version of QuicksyServer

This reverts commit d0a2f1f4.

Unignored gradle.properties since androidX requires additions there
See also https://developer.android.com/jetpack/androidx/migrate

This reverts commit f23016c9.

this attribute is mandatory as per the XEP.

DIGEST and HMAC were static variables. Those are initialized by
what ever concrete implementation gets executed first.

(Perform SCRAM-SHA1 first and those variables got initialized with
SHA1 variants)

For subsequent SHA256 executions those variables contained wrong
values.