Final cleanup of cpus-per-proc for 1.7.4 - provide better checking for cpus-per-proc and mismatched mapping/binding directives, and provide error messages telling the user what to do to get it right.

cmr=v1.7.4:reviewer=jsquyres
Make clear that --with-pmi can/should be used to specify the path to the pmi installation since at least one person didn't realize it.

cmr=v1.7.4:reviewer=jsquyres