Feature/Space.configuration API for passing server-set value to the client in Meteor.settings

In this PR https://github.com/meteor-space/base/pull/23 I introduced a pattern for [passing down configuration](https://github.com/meteor-space/base/blob/develop/source/configuration.js#L15-L25) set on the server to the client via Meteor.setting.public. The scope of this feature is to make an API to allow additional configuration options to be managed from external packages even.
