doc: announce OF1.4 support in README

We support good a good portion of OF1.4.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
of14: remove of1.2/1.3 old SetField aciton API

No reason to support the old awkward API for shiny OF1.4.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
of14: set default ethernet types for MPLS actions

0x8847 (MPLS) for PUSH_MPLS
0x0800 (IP) for POP_MPLS

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
of14: default ethernet type for PUSH_VLAN action

0x8100 in most cases.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
of14: Fix OFPInstructionMeter json format

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>