add help messages and defaults to AC_ARG_VAR variables
openlavadmin -> openlavaadmin (typo corrected in all cases)

Signed-off-by: Roy Storey <roy.storey@plantandfood.co.nz>
making the AC_ARG_VAR(openlavacluster) useful WRT config and ${prefix}/etc/lsf.cluster.NAME

Signed-off-by: Roy Storey <roy.storey@plantandfood.co.nz>
Merge pull request #51 from kiwiroy/ac_arg_var-with-defaults

AC_ARG_VAR with defaults and lsf.cluster.CLUSTERNAME file