Cleanups related to new service providers

* Some refinements in the thumbs module
* Implement thumbs and avatar services in publisher
* Some refinements to Avatar service to improve utility
* Add 'service' type to to Xoops\Module\Admin->addConfigBoxLine so modules which depend on a service can check that a provider is installed (i.e. 'images' depends on a 'thumbnail' service)
Some minor cleanups
Merge pull request #171 from geekwright/cleanup

Cleanups related to new service providers