Correcly handle documentation in subdirectories

* Allow empty FileHandle/SocketHandle etc instances
* Make ServerSocketHandle::listen depend on AddressingPolicy
* Replace all occurences of inet_ntoa with inet_ntop (thread safety)
* Fix handling of exceptions in ReadHelper/WriteHelper
* Fix Scheduler ERR/HUP semantics

Ipmlemented more compatible, standards conformant and flexible ClientSocketHandle::read() and readfrom() members

More layout fixes using XSLT

Unified emacs Local Variables

Further Socket library documentation

Updated documentation templates to include cross-reference
Fixed documentation build (especially regarding cleanup)
Cleaned up BUG, FIXME, TODO and IDEA items
More SocketLibrary documentation

Renaned directory satscons to senfscons

add missing retrive_filehandle overload
fix operator bool (use safe bool idiom)
add GenericSockAddr as default Address implementation

started ClientSocketHandle generic interface