Finish wiring up requests for webservd

Also, change HttpRequest to a binder rather than a parcelable so that
responding to a request can be done via a method on the request itself,
rather than a random method elsewhere that needs a GUID to correlate.

Test: Build continues to pass. We'll have full tests when libwebserv
      catches up.
Bug: 26914456
Change-Id: I732c135e3502e4808de8a36691b89b8931c343d1
11 files changed