Adding new tutorials

[aaron-613]

As part of long-overdue CSF work, finally checking in Markdown versions of the new tutorials. They will include:

• HelloWorld
• Direct Pub/Sub
• Direct Processor
• Direct Request/Reply
• Guaranteed Pub/Sub

Not every API will have the full set, but eventually they should.

[TamimiGitHub]

Note: Added the NewGen Java/Python/Go hello world tutorials in a separate commit here 6fc186b