Fix bug in HTTP server: GET Content-Type

Was incorrectly detecting that a Content-Type header was supplied
with a GET request, when in fact none had been supplied
Implement HTTP GET /restful/rhizome/<BID>.rhm
Merge branch 'development' into 'naf4'
Improve HTTP server string reservation

So that reserved strings can be released, reclaiming buffer space for
responses and for response header strings
HTTP server support for extra response headers
Add Rhizome HTTP response headers to /restful/rhizome/<BID>.rhm
Implement HTTP GET /restful/rhizome/<BID>/raw.bin
Unify output manifest fields from CLI rhizome commands
Improve test case for /restful/rhizome/<BID>/raw.bin

Include some encrypted payloads in the test
Refactor HTTP server result code handling

Rhizome dispatch functions now simply return the HTTP result code, or 1
if they have initiated the response themselves.
Implement HTTP GET /restful/rhizome/<BID>/decrypted.bin
Fix strn_to_sid_t(), add strn_to_rhizome_bk_t()

Improve strn_to_rhizome_bid_t() and strn_to_rhizome_filehash_t() to
accept a NULL first arg -- useful for data validation
Remove some unconditional debug from HTTP server
Log error in "rhizome extract" if payload fails
More Rhizome external blob debug
Fix rhizome_fill_manifest() 'name' semantics

Only set 'name' field if the given pathname is valid

Do not set 'name' field if no pathname supplied
Improve 'rhizomehttp' test descriptions
Improve read_whole_file()

Move into os.c, declare and document in os.h
Improve test framework: assertGrep --ignore-case
Remove rhizome_read_manifest_file()

Replace with memcpy() followed by rhizome_manifest_parse()
for memory buffers

Replace with rhizome_read_manifest_from_file() for files