Generic args passing

Added support for passing of arguments throughout the Tinia infrastructure
* updated html/javascript in static pages to have an arguments-field
  which is parsed and shipped to mod_trell.
* updated schema to allow a set of <args>-tag's in addjob.
* rewrote fork/exec-parts of mod_trell and master job,
  as well as receiving end in IPCController to use environment variables
  instead of arguments to set job id etc.

  The part of mod_trell that performs fork/exec etc. was rewritten to use
  the platform-independent APR-interface. However, there doesn't seem to
  be support for globally named semaphores/mutexes, and hence porting all
  IPC-stuff to APR is not possible without resorting to other classes of IPC-primitives.

  The old behaviour of mod_trell was to pass the full apache-environment along to
  master-job, which in turn passed it to the jobs. New behaviour is to only pass along
  PATH and LD_LIBRARY_PATH to master job, and master job passes along its full
  environment except the TINIA_-variables. An idea is that the PATH and LD_LIBRARY_PATH
  for the tinia executables could be set in the http.conf to get full control.