[fsmgracoll] Add types.py with common types mapping

Signed-off-by: Anton D. Kachalov <mouse@yandex-team.ru>
[fsmgracoll/snmp.py] Import types from types.py

Signed-off-by: Anton D. Kachalov <mouse@yandex-team.ru>
[fsmgracoll/agent.py] Cleanup

Signed-off-by: Anton D. Kachalov <mouse@yandex-team.ru>
[fsmgracoll/__init__] Import all stuff

Signed-off-by: Anton D. Kachalov <mouse@yandex-team.ru>
[fsmgracoll/ipmi] Add no-op `on_disconnect'

Signed-off-by: Anton D. Kachalov <mouse@yandex-team.ru>
[fsmgracoll/snmp] Cleanup

Signed-off-by: Anton D. Kachalov <mouse@yandex-team.ru>
[requirements.txt] Add `python-fsmodbus'

Signed-off-by: Anton D. Kachalov <mouse@yandex-team.ru>
[cfg/metrics] Update examples

Signed-off-by: Anton D. Kachalov <mouse@yandex-team.ru>
[fsmgracoll] Add Modbus* agents

Signed-off-by: Anton D. Kachalov <mouse@yandex-team.ru>