(flx:refac): changed from compile time to runtime selection between
flexpath transport/reading method and mpi transport/reading method;
removed some redundancy
Merge branch 'v1.5.1' into mag-v1.5.1
(flx:refac): changed compile-time determination of transport/read method
to runtime (option -t flx, or -t mpi) for maya_append; minor cleanups of
the code (removed redundant variables)