Update release notes for 18.1 (sdnfv#238)

* Update release notes for 18.1

* Update Releases.md

17.11 readme and release notes (sdnfv#228)

Updating release notes and readme for Release 17.11

Commit Log:
* update year in license

* Update readme and release notes for v17.11

* Add ONVM citation to readme

* typo in releasesgs

* Release headline

* lowercase openNetVM

* move arp to example list

Provide Interface for NF to get TX/RX Rings (sdnfv#164)

This provides a new interface for NFs to get data from the manager.  Instead of being limited to the traditional model where an NF asks the ONVM manager for packets, this addition enables an NF to have direct access to its TX/RX rings and its stat's structure.

Commit log:
  * Extend nflib NF API to accomodate Snort DAQ NF requirements.
  * Only allow a single NF Mode
  * Update NF dev documentation about dual interfaces
  * Give SpeedTester option to run with direct rings

ONVM library (sdnfv#157)

These changes build the ONVM code as a library which can more easily be included with NFs.

Commit log:

* Create proper library for onvm_nflib, rename common.h to be less common.
* Include all shared files in the library, rename library libonvm.a.
* Make dequeing from NF rings simpler.
* Syntax cleanup
* Updating AES NF's Makefiles to use library

Refactored, cleaned up, and changed API (147)

Refactoring to improve code organization

A big set of commits to clean the structure and simplify onvm source
code.

We separated all functions into the main.c of the manager into modules :
 - `onvm_stats` : functions displaying statistics
 - `onvm_pkt` : functions related to packet processing
 - `onvm_nf` : functions related to NFs management.

Each module comes with a header file with commented prototypes. And each
c and h file has been "cut" into parts :
 - interfaces, or functions called outside of the module
 - internal functions, the functions called only inside the module and
   doing all the work
 - helper functions, simple and short functions used many times through
   the module.

**API Changes:**
 - NFs now need to call functions like `onvm_nflib_*` instead of
   `onvm_nf_*`.  For example, `onvm_nflib_init` instead of
`onvm_nf_init`.  The example NFs have all been updated accordingly.
 - NF `Makefiles` need to be updated to find the path to `onvm_nflib`.

Documentation fixes (sdnfv#145)

Fixes typos for environment variable and run scripts.