network: unified wired connection name

- update po
- set device speed to unkown if is 0
- add strToUuid(), used for generating connection
- add general method to get device vendor
  uuid for wired devices
- refactor code, return error instead of bool for some
  nm utils functions, include nmGetConnectionById and
  nmGetActiveConnectionByUuid

tower: https://tower.im/projects/8f19f0bf0e754f0b82ef2c24bc230973/todos/7644b485880348508f8095ba0a59578b/

Change-Id: I39daacf4f4b91df6c860778be1836a05dd8179f6