Add aliases to drmemtrace launching: "-t drmemtrace" and "-tool"

[derekbruening]

Today all drmemtrace analysis tools are launched with a front-end named "drcachesim" and with a tool selector named "-simulator_type". Those names can be misleading. We should add aliases and update the docs so the invocation changes from:

bin64/drrun -t drcachesim -simulator_type reuse_distance ...

to:

bin64/drrun -t drmemtrace -tool reuse_distance ...