Minor polishing in http space, to get them out of substantial change
to follow shortly.
Introduce a dedicated http_SetStatus() function.
Polish up HTTP1_DissectResponse()
Always set the reason headerfield when the status field is set, to
keep them in sync.  If you want a custom reason field, set status
first, then reason.

With this in place, HTTP1_Write() doesn't need to worry about them
being OK, and we can polish that code a fair bit.

Turn a couple of boolean arguments into more readable magics.
Docfix an erroneous reference to r-r director having weight.

Fixes: #1519
Fix minor double wording.
Name directors consistently for clarity.

Using multiple names for the instanciateed directors in this document
just makes it more confusing, since .add_backend() and .backend() is
mostly identical for all of them.
Rewrite director descriptions.

Add a bit more detail while cleaning up the language.

Reformat for tabs instead of 7 spaces.
Rememeber to supress body if we do 304 conditional response.

Fixes	#1518
Merge branch 'master' of git.varnish-cache.org:varnish-cache