readable/writeable not optional arguments (lead to confusion)
forward declare HSObject, not strictly available
method for splitting a path into its elements
attribute_.h needs to be included by itself
implement typestr(), add HOOK type
make accessors for reading/querying const
store pointer to self
accessors to children, attribs and actions
remove header dependency
hook system
a print method for debugging
a test class for the new object design
Merge branch 'winterbreeze' of https://github.com/herbstluftwm/herbstluftwm into winterbreeze

Conflicts:
	src/testobject.cpp
	src/testobject.h