This adds a gradle task called generateContextDoc in the Painless module. The
task will start a cluster, issue commands against the context rest api for
Painless, and generate documentation for each API per context. Each context
has a first page of classes sorted by package first and class name second,
along with a page per package with each classes' constructors, methods, and
fields. A link is generated for each constructor, method, and field to a JavaDoc
page when possible.
Links to inner classes were using `$` in urls instead of `.`, causing
them to 404.
Also fixes the doc generation code to generate docs into the correct
directory. We moved the docs but never updated the generation code.
Jack Conradson
Nik Everett
debadair