Initial version of a new proxmox plugin + some changes required by it.
Got rid of proxmoxer, which gives different results for proxmox 2 vs 3.

'Force autoscan' is now triggered only when SNMP name is missing.
Added possibility to work in restricted environments (i.e. where there
is no access to web api) + some misc improvements.

Improved disk shares' matching with their pvs.
Added tests.
Code review fixes + added docs + fixed some typo in docs.
Merge pull request #1169 from xor-xor/feature/proxmox

New scan plugin for Proxmox 2 and 3.