doc: update many bash examples that used old-style flags.
Review Request #1377 - Created Nov. 21, 2014 and submitted
some of these had become lies;
some of these still work, but now seem strange
excellent feedback is excellent; Zundel caught a "bundel".
Also, another fix that was hiding in an unsaved Emacs buffer:
./pants goal foo --explainis now
./pants goal --explain foo
Revision 2 (+48 -51)