view: consolidate whitespace stripping from messages

view: consolidate whitespace stripping from messages

We now keep intermediate blank lines in messages, since it
could be used to denote logical gaps in the message
(such as giving readers a chance to opt out of "spoiler"
information).

However leading blank lines, trailing blank lines, and
trailing whitespace have no useful value we can discern;
so drop those entirely to prevent clients from eating up
vertical whitespace.