Remove whitespace from blank lines

Also renamed "objects" to "entities" in some action methods, to match
the selectors.
Add pause and show contents action; allow actions to return a single
message

Show contents is a fairly complicated function, as it's the only one
that really requires some text formatting.

It's also the first to have some keyword options. Still need to
implement that in the actual datafile.

Also added some text attributes on nouns and rooms.
Increase maximum line length to 100 characters

Also reduce maximum docstring length to 72 (but enforce loosely).