Removed full license header in **/*.{asd,lisp}

* {src,test}/*.lisp (header): updated copyright; removed full license
  header
* jenkins.api.asd: likewise
Cleaned up slots of exported model classes in src/api/{classes,package}.lisp

* src/api/classes.lisp (define-interface-implementations publisher):
  added some initial slots for ssh and warnings publishers
  (define-model-class job): cleaned up slots
* src/api/package.lisp (package jenkins.api): sorted and commented
  exported symbols; added exported symbols for publisher interface