opal: add mca param to control ranks env variables

add -mca base_env_list "var1=val1 var2=val2 ..." mca parameter that can be used in mca param files
or with -am app.conf mpirun commandline to set rank env variables with mca mechanism

fixed by Elena, reviewed by Miked

cmr=v1.8.1:reviewer=ompi-rm1.8
Java: move buffer methods from Comm.c to MPI.c