Ensure environment variables match the Framework Spec

[mraible]

The Node.js docs use:

export STORMPATH_CLIENT_APIKEY_ID=YOUR_ID_HERE
export STORMPATH_CLIENT_APIKEY_SECRET=YOUR_SECRET_HERE
export STORMPATH_APPLICATION_HREF=YOUR_APP_HREF

While we support:

STORMPATH_API_KEY_ID
STORMPATH_API_KEY_SECRET

We should support STORMPATH_CLIENT_APIKEY_ID according to https://github.com/stormpath/stormpath-sdk-spec/blob/master/specifications/config.md

I think this needs to be changed in DefaultEnvVarNameConverter.java, possibly in other locations too.