restore default constructor argument
SolutionTransfer as ParallelObject
Adding a FakeCommunicator class
Add --enable-default-comm-world argument

This is just the build system bit; the next patch will change behavior
in the --disable-default-comm-world case.
Just move tiny FakeCommunicator into parallel.h
Communicator_World -> this->communicator() fixes
Add missing header for START_/STOP_LOG
perflog isn't in libmesh.h anymore
Implement DISABLE_COMM_WORLD

Also get rid of deprecated init()/close() functions; we're going to
want a Communicator to be part of LibMeshInit objects
Merge branch 'communicators' of github.com:roystgnr/libmesh into communicators