Add Selectors for Transcluded Content

Transcluded content may not fit nicely into the target location by adding or removing margin or padding. Thus the content is not easily to read.

We need to add selectors to allow users to adjust any inconvenient margins/paddings by selecting only on transcluded content.

Therefore each transclusion macro should add a class to the container rendering the transcluded content. This class is "projectdoc-transcluded-content".

This additional class would be provided by transclusion macros such as the Transclusion Macro and the Transclude Documents Macro.