Symlink other executables for client

[twavv]

Seems like some other things should be linked (in particular, I was looking for ysql_dump).

[benk-gc]

Another request for adding utilities like ysql_dump, ysql_dumpall, and ysql_bench as symlinked commands - this is very useful to have access to on host systems and having them only in the Cellar directory doesn't seem to let me symlink them myself in a portable manner since brew doesn't provide a way to do this irrespective of the installed version.