Yes, the ServiceContent and there is a "Settings" property which contains key/value pair.
If you're building a vSphere Web Client plugin, there's documentation on how you should register and deploy your plugin. You may also want to post your question in the vSphere Web Client Forum http://communities.vmware.com/community/vmtn/developer/forums/viclientplugins I know there are a few VMware developers from our vSphere Web Client team that monitor that forum and you can get more details on the best way for packing/registering your plugins.