Minor reorganization of broctl README to avoid redundancy

Reorganized a few sections of the document to avoid having the same
information in multiple locations.  Made the use of prefix more consistent
in the examples.  Corrected several typos.
Merge remote-tracking branch 'origin/master' into topic/dnthayer/doc-updates
Merge remote-tracking branch 'origin/topic/dnthayer/doc-updates'

* origin/topic/dnthayer/doc-updates:
  Minor reorganization of broctl README to avoid redundancy