of1.2, of1.3: update document for OFPMatch

ofproto_v1_3_parser.OFPMatch:
  add a list of available fields.
ofproto_v1_2_parser.OFPMatch:
  add docstrings same as of1.3.
doc:
  add reference page for of1.2

Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
doc: fix overflow from the page in latex/pdf.

Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
lib/packet: update docstrings to fix broken tables in latex/pdf

Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>