Add CRUD support for Flux modules

Flux modules are nearly API complete. We need to a way for users to publish and interact with modules on release day and the CLI is the best option. To keep implementation simple we want to start with the following verbs:

influx module list
influx module publish
influx module download 
influx module versions 

List

influx module list should list all modules and their latest version

Publish

influx module publish should take a directory and build the Flux code within the directory and then upload the directory if the build succeeds. We need to define precisely what build means, but it will likely be compiling all the code to semantic graph and ensuring no errors.

Download

influx module download should download a zip file of a specific module and a specific version. Support for @latest and @pre should be included.

Versions

influx module versions should list all versions for a given module

Start by mapping the CLI entry points for module list, publish, download, and versions. Clarify what publishing builds, how module and version arguments work, and how @latest and @pre resolve; done means all four commands meet those behaviors and publish only uploads after a successful build.