Pktgen documentation updates

[sreyanalla]

Summary:

Improves the existing Pktgen installation guide by providing clarity on Lua installation. Pertains to #181 , which requests Pktgen documentation updates.

Please see Pktgen Wiki page, which fully resolves the issue mentioned above.

This PR includes
Resolves issues	#181
Breaking API changes
Internal API changes
Usability improvements
Bug fixes
New functionality
New NF/onvm_mgr args
Changes to starting NFs
Dependency updates
Web stats updates

Merging notes:

• Dependencies: None

TODO before merging :

• [X] PR is ready for review

[onvm]

In response to PR creation

CI Message

Aborting, need an authorized user to run CI