mdcore Code

added SPU code, still need to find a way to activate this through the configure script.

added new error reporting mechanism, removed old variables.

updated TODO-list.

made SHAKEing of water molecules parallel with OpenMP.

added more elaborate error reporting and SSE-enabled vectorized potential evaluation.

added functions to register particle types and potentials.

updated TODO list.

added specific btree testing program.

added btree for mapping virtual to local ids and errs for better error reporting.

added TODO.txt listing some problems that need solving.