Store node pointers in Side

This means that get_node(), point() can now be much simpler and can be
inline instead of virtual.
Avoid allocation in dof_indices()

We may need a temporary vector in the TRI3SUBDIVISION case but we can
avoid it in the common case
Close up PerfLog on every function return

This fixes a miscellaneous_ex11 bug with PerfLog enabled
Reduce some variable scope
Merge nested if statements
Cache some accessor results

This may be overkill, but I don't think it's *theoretically* overkill;
we call non-inline functions in between these accessor calls and so
even though we can be sure the results haven't changed, the compiler
probably can't.
Only assert scalars are scalars in dbg mode
Cache SCALAR dof index locations in DofMap
Internal assertion in new SCALAR_dof_indices code
Merge pull request #412 from roystgnr/dof_indices_optimize

Dof indices optimizations