allow to unset single value headers (such as content-length).
have portal servlet handle chunked encoding according to servlet spec.
cosmetics.
add accept-ranges and utility methods on transfer-encoding.
add accept-ranges and utility methods on transfer-encoding.

Conflicts:

	src/main/scala/servlet/PortalServlet.scala
change DataSourceBody to StreamBody and make Body sealed.
Merge branch 'bodyMapping' into chunked
refactor StreamBody into a trait and a concrete Implementation (InputStreamBody).
Change semantics of discard to no exception if already consumed (or discarded).
Merge branch 'bodyMapping' into feature/chunked
test for streamed and huge data.
fix read in test.
fix map for body to properly handle the consumed flag (from the mapped).
better handling of Option in non-Option Header.
Merge branch 'master' into feature/chunked

Conflicts:
	src/main/scala/http/headers/Header.scala
fix the huge data test.
add test for in-memory without content length set.
change GZipCompressor to allow for non-in-memory compression.
fix bug in test (missing now()).
define behaviour on streamed/chunked input.