[IM] de-inexify peering manager - fixes #180

Documentation updated at:

https://github.com/inex/IXP-Manager/wiki/Peering-Manager
Version bump
[HK] Renamed to prevent overwrites for people who use it in place.
[IM] Remove confusing link to non-SNMP switch add method
[IM] Discourage manaual addition of switches
[BF] Fix regression - fixes #186