Bug #1126352
This patch introduces a simple framework for enabling
nvlib to call the appropriate routine according to the
current version. To this aim, we leverage the 'server' header
which is returned by every NVP API calls (except login/logout).
The patch also accounts for the changes introduced in NVP 3.0
Change-Id: Ief3a6f2b5b99ea33548353ce3bee3fa23e42752f