Dissect HTTP/2 draft-13

Summary of changes since draft-12:

* Pad High and Pad Low wereare replaced with single Pad Length field.
* Padding was removed from CONTINUATION frame.
* ALTSVC and BLOCKED frames were removed.
* Per-frame compression and its associated SETTINGS flag were removed.
* HPACK Huffman code table and static header table were updated.

Change-Id: I9c4f05f8cd937bfadbb1b912f2b9ffb31e9c18d5
Reviewed-on: https://code.wireshark.org/review/2615
Reviewed-by: Evan Huus <eapache@gmail.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>