Cleaned up file headers and AUTHORS file

* AUTHORS: removed; not very useful
* src/types.lisp (header): updated copyright; removed license text
* src/conditions.lisp: likewise
* src/protocol.lisp: likewise
* src/append-nodes-mixin.lisp: likewise
* src/compat.lisp: likewise
* src/construction.lisp: likewise
* src/conversion.lisp: likewise
* src/create-missing-nodes-mixin.lisp: likewise
* src/ignore-empty-results-mixin.lisp: likewise
* src/lisplab.lisp: likewise
* src/local-time.lisp: likewise
* src/location.lisp: likewise
* src/multi-location.lisp: likewise
* src/singleton-location.lisp: likewise
* src/variables.lisp: likewise
* src/xpath-creation.lisp: likewise
* src/macros.lisp: likewise
* src/package.lisp: likewise
* test/append-nodes-mixin.lisp: likewise
* test/conversion.lisp: likewise
* test/create-missing-nodes-mixin.lisp: likewise
* test/ignore-empty-results-mixin.lisp: likewise
* test/lisplab.lisp: likewise
* test/local-time.lisp: likewise
* test/location.lisp: likewise
* test/multi-location.lisp: likewise
* test/macros.lisp: likewise
* test/package.lisp: likewise
* xml.location-and-lisplab.asd: likewise
* xml.location-and-local-time.asd: likewise
* xml.location.asd: likewise