Feature: Allow literal-include of arbitrary project files

[marble]

Situation

Documentation usually is only a part of a total project with relevant files only in the root folder PROJECT/ and the subfolder tree at PROJECT/Documentation. So our container usually only cares about the root folder and the Documentation/... tree. This is done by intention, as project may happen to be huge.

Desire

Sometimes it would be nice, however, if the documentation could refer directly to real project files lying outside documentation, so there could be includes like .. literal-include:: /PROJECT/Php/Classes/...

Implications

This is conceivable, if the rendering toolchain at some point checks the include directives (which is already done any way) and copies those external, referenced project file into the documentation.