Kill dead ide templates
Lay the groundwork for less ivy configuration wrangling.

Dynamically map confs in-play in generated ivy.xmls.
Pull conf specification requirement out of pants.ini by defaulting in many locations.
Fixup JarDependency.with_docs and add support for fetching javadoc to IdeGen and use this in IdeaGen - no EclipseGen support for now.
Push ivy conf handling into IvyUtils - automatically setup ivy ops to use a specified set of confs.