filepath.Walk does not follow symbolic links.
There's no easy fix for that outside of Go, so the best we can do for now is to give notice to the end user by ERROR log statements.
This commit also fixes a related panic situation in GenerateTemplateNameFrom when the layout dir was a symbolic link.
Fixes#283
filepath was used inconsistently throughout the hugolib. With the
introduction of source and target modules, all path are normalized to
"/". This simplifies the processing of paths. It does mean that
contributors need to be aware of using path/filepath in any module other
than source or target is not recommended. The current exception is
hugolib/config.go
