support jquery style element / css style / id lookups of elements on a document/element - along with test cases

 #KT-1267 fixed
 #KT-1271 fixed

refactored the templates to make use of the lovely new multi line strings with templates; they're much easier to read now in IDEA (further improvements could be done to refactor functions from printFoo() to be foo() returning the String of the result)

added links to the extension functions from the summary page table and fixed up the detail extension function docs (also made nice use of the multi line treble quoted strings with templates, yay! :)

refactored the kdoc implementation to introduce a Doclet trait so its easy to plugin new documentation generators or use different templates etc

KT-1219 Incorrect 'unused value' error in closures

added a notEmpty() method to String? so its polymorphic with Collection? too; its easy to tell if a string/collection is not null and not empty

include all inherited extension functions; so Collection / List extension page shows all available methods

added collection.toSortedSet() for easier conversion to sorted setsand collection.notNull() so its easy to treat a nullable collection/list as a collection

 #KT-1317 fixed

 #KT-1374 fixed