Allow Contrib libs to exclude JDKs and Clojure versions

New ci_data.clj options for matrix test builds of contrib libraries:

  :min-clojure  Clojure version string like "1.3.0", the minimum
                version this library supports. Matches strings in the
                :clojure-versions list

  :exclude-jdk  Set of JDK names like "IBM JDK 1.5" to exclude from
                the matrix build. Matches :name strings in the :jdks
                list.