Implement serial execution in MPI

In order to implement serial execution in MPI, two additional
functions have to be exposed through the API interface
(serializeBeginExec and serializeEndExec).
Change function names to more appropriate names

on_current_process => onLocalVM
get_process_id => getVMId
Abstract database print and dump to API

For consistency and testing reasons, the database print and dump
should be predictable, which only the API can guarantee in
multi-process asynchronous layers (such as MPI).