Add config.xml

* TQSL config.xml version 2.5; last updated 2013-10-02 15:57Z
  see <https://lotw.arrl.org/lotwuser/config.tq6>

* NOTE WELL: how to convert config.tq6 into config.xml
    1. `gunzip -c config.tq6 > config.xml`
    2. Remove `<tqsldata>` tags
Update README.md

* Added details on config.xml
Update config.xml

* Based on Version 2.6; last updated 2013-10-14 12:04Z
* See <https://lotw.arrl.org/lotwuser/config.tq6>
Remove TrustedQSL, update README.md