addrconv: binary <-> text conversion of mac/ipv4/ipv6 addresses

implemented as a simple wrapper of netaddr.

background:
    the goal is to use the consistent representations of addresses
    throughout the tree, instead of the current ad-hoc representations
    like a list of int16 for ipv6 address.

    - netaddr style text (eg. '10.0.0.1', 'ff02::1') for ryu-app level api.
    - on-wire binary for internal use.

    this is the first step to the direction.  ie. have a single
    implementation of address representation conversion.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
addrconv: replace bin<->text converters for mac addresses

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
addrconv: replace bin<->text converters for ipv6

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
addrconv: use bytes instead of int to represent ipv4 addresses

change ipv4 representation from int to bytes in many places.
replace homegrown bin<->text routines with addrconv for ipv4.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
rest_router: follow packet lib api change

packet lib now uses bytes, not int/long, to represent ipv4 addresses.

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